GRFSpecs - User contributions [en-gb]

Standardized Railtype Scheme extensions

2025-09-27T17:31:15Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||e, then v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|e ||Maglevs that use a synchronous linear induction motor (EDS) ||I ||(Electrodynamic) Requires onboard supercooling ||CRRC (TACe)
|-
|W ||VacTrain with linear induction motor track (EMS or EDS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||v, then U ||
|-
|6 ||600v DC catenary ||v, then U ||
|-
|v ||750v & 600v DC catenary ||U ||Combines both necessary voltages of 600mm catenary.
|-
|z ||25kV AC catenary & 750v 3rd Rail ||U ||Used in New York City on the New Haven Line.
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||Not applicable ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-23T00:52:45Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||e, then v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|e ||Maglevs that use a synchronous linear induction motor (EDS) ||I ||(Electrodynamic) Requires onboard supercooling ||CRRC (TACe)
|-
|v ||VacTrain with linear induction motor track (EMS or EDS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||v, then U ||
|-
|6 ||600v DC catenary ||v, then U ||
|-
|v ||750v & 600v DC catenary ||U ||Combines both necessary voltages of 600mm catenary.
|-
|z ||25kV AC catenary & 750v 3rd Rail ||U ||Used in New York City on the New Haven Line.
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||Not applicable ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-23T00:52:14Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||e, then v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|e ||Maglevs that use a synchronous linear induction motor (EDS) ||I ||(Electrodynamic) Requires onboard supercooling ||CRRC (TACe)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||v, then U ||
|-
|6 ||600v DC catenary ||v, then U ||
|-
|v ||750v & 600v DC catenary ||U ||Combines both necessary voltages of 600mm catenary.
|-
|z ||25kV AC catenary & 750v 3rd Rail ||U ||Used in New York City on the New Haven Line.
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||Not applicable ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-23T00:26:04Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||v, then U ||
|-
|6 ||600v DC catenary ||v, then U ||
|-
|v ||750v & 600v DC catenary ||U ||Combines both necessary voltages of 600mm catenary.
|-
|z ||25kV AC catenary & 750v 3rd Rail ||U ||Used in New York City on the New Haven Line.
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||Not applicable ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-22T23:57:45Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U ||
|-
|6 ||600v DC catenary ||U ||
|-
|z ||25kV AC catenary & 750v 3rd Rail ||U ||Used in New York City on the New Haven Line.
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||Not applicable ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme

2025-08-22T23:49:32Z

0n3!r0!: /* Energy source type class [***X] */

This railtype label scheme aims to provide a way to allow players to easily mix and match different train and track sets. It does this by grouping the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track type and gauge, speed class, allowable axle weight and electrification type. To limit combinatorial explosions of rail types, the track properties are abstracted away from strict real-life representations.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set. Additionally, due to the decoupling, depending on the specific train and track sets used, not all defined vehicles and/or track types might be available in a specific set combination. This is fully intended behaviour.

== When to use the scheme and when ''not'' to use the scheme ==

When to use:
* If you only want to develop a track or a train set.
* If you want players to be able to mix-and-match sets.
* If you are okay with abstractions from real life.

When ''not'' to use:
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track type and gauge class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track type and gauge class [X***] ===
The first position in the railtype label defines track type and/or track gauge class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

All track types or gauges are abstractions of real-life types and do not correspond to specific examples used in real-life. For example '''N''' is any gauge that is smaller than standard gauge, but not corresponding to any specific gauge that exists in real life, just like '''n''' is smaller than '''N''', but does not corresponds to a specific real-life gauge.

A train set may define vehicles for gauge '''n''' while not defining vehicles for gauge '''N''', but this is likely only useful for sets that are specifically designed to be used along-side other sets, and the used railtype fallbacks should be carefully considered.

=== Speed limit/appearance class [*X**] ===
The second position in the railtype label defines the speed limit/appearance class. This can be used to provide tracks with different speed limits or appearance variations. The speed limit/appearance class is ''not'' used for trains and a train set should always use the class letter '''A''' in this position.

There is no fixed numeric mapping for this class, but speed limits should start at '''A''' for the lowest speed limit and progress with '''B/C/...''' for higher limits. If you do not want to employ speed limits in your track set, always use the class '''A'''.

Additionally this class can also be used to distinguish different track appearances like normal or full width ballast, grass or concrete ground, etc. Train sets must not define vehicles for appearance classes. If you think you have special vehicles that should only run on the appearance class, it is ''not'' appearance but a separate track type/gauge.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a higher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track type/gauge and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Ideally, all five standard axle load classes should be used, but a train set may use only some weight classes, as the vehicle rooster might not make it feasible to use all five. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. If you do not use all classes, try to spread the classes out (don't use '''A''' and '''B''' for two classes, but e.g. '''B''' and '''D''').

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existence of any other class than '''A''' through '''E''', so think about providing appropriate fallbacks in your railtype table. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First D, then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

All energy source types are abstractions of real-life types and do not correspond to specific examples used in real-life. For example '''D''' and '''d''' are treated as two different DC voltage levels, but do not correspond to any specific real-life voltage level used.

A train set may define vehicles for energy source '''d''' while not defining vehicles for energy source '''D''' (as an example, applies to other energy sources, too), but this is likely only useful for sets that are specifically designed to be used along-side other sets, and the used railtype fallbacks should be carefully considered.

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary and notes for track sets ==
This section summarizes and comments the above for track sets.

; [X***] Track type and gauge class
* Define at least one track type for every track type/gauge class you want in your set.
* If you only provide tracks for one type/gauge, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
* Don't use specialized sub-types (e.g. d, a) unless you also use the main specialized class (e.g. D, A).
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always re-define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent label(s) from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
; Powered/compatible rail types
* For the speed limit/appearance class, every type should be powered and compatible with each other.
* Axle load classes implemented as real railtypes should be powered and compatible in ascending order, i.e. a lower axle load is compatible with a higher axle load, but not vice versa.
* Different energy sources should be compatible with each other but not powered on each other, expect for multi-system energy source classes.
* Different track type and gauge classes should be neither powered nor compatible with each other.

Or, put differently, for each type/gauge, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary and notes for train sets ==
This section summarizes and comments the above for train sets.

; [X***] Track type and gauge class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
** Think about your set design and how for example standard gauge and narrow gauge vehicles differ to decide if a fallback from narrow gauge to standard gauge has gameplay meaning.
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded. This is a decision you need to make depending on the design of your train set.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations. This can mean that some vehicles may not appear with some set combinations, but if a player does not want to have e.g. narrow gauge tracks, they might not want narrow gauge vehicles either.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

==Extensions and best practice==
See [https://newgrf-specs.tt-wiki.net/wiki/Standardized_Railtype_Scheme_extensions Standardized Railtype Scheme extensions]

Standardized Railtype Scheme extensions

2025-08-22T23:44:28Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of their railtypes.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U ||
|-
|6 ||600v DC catenary ||U ||
|-
|z ||Atypical catenary voltage ||U
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-22T23:43:33Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||[[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] would need to contain literally everything you can think of, so instead developers of track sets should always add "_R_t" to the [[NML:Railtypes#Railtype_properties|compatible_railtype_list and powered_railtype_list (NML)]] of your railtype.
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U ||
|-
|6 ||600v DC catenary ||U ||
|-
|z ||Atypical catenary voltage ||U
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-22T23:36:47Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks); improbable, but not physically impossible ||E ||
|-
|8 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, 3-phase catenary (literally had 3 cables) and universal catenary (SA_E); a total of 5 rails (2 for wheels, 3 for electricity; plus 3 overhead catenary lines equals 8) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U ||
|-
|6 ||600v DC catenary ||U ||
|-
|z ||Atypical catenary voltage ||U
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||N/A ||
|}

Standardized Railtype Scheme extensions

2025-08-22T22:30:14Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal "no energy" type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback to a "***-" label, or add a "***-" label to any [[NML:Railtypes#Railtype_properties|compatible_railtype_list, powered_railtype_list or alternative_railtype_list (NML)]], this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-22T22:24:22Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put both "***N" and "***E" in the [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]] of a "***-" label, but neither under the [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]]) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T19:15:42Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes !!Examples
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling ||SCMaglev (LABS)
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling ||"JR-VacLev" (fictional, LABV)
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power ||Transrapid (TABI), Linimo (LABI)
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power ||"Vacrapid" (fictional, TABv)
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T19:09:59Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor (EMS) ||v ||(Electromagnetic) Relies on track power
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T19:09:16Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track (EDS) ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic) Relies on track power
|-
|v ||VacTrain with linear induction motor track (EMS) ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T19:08:36Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic) Relies on track power
|-
|v ||VacTrain with linear induction motor track ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic Suspension) Relies on track power; Unpublished, likely used for Linimo (JP+)
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T18:53:46Z

0n3!r0!: Fixed to reflect current Maglev Track Set.

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear induction motor (EDS) ||V ||(Electrodynamic) Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor (EMS) || N/A ||(Electromagnetic) Relies on track power
|-
|v ||VacTrain with linear induction motor track ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Linear induction motor || D ||Correct usage; despite the names suggesting the opposite, linear induction is not used by Transrapid, only by SCMaglev
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T17:44:21Z

0n3!r0!: /* Energy source type class [***X] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||V ||Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor || N/A ||Relies on track power
|-
|v ||VacTrain with linear induction motor track ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|I ||Linear induction motor || D ||Correct usage; despite the names suggesting the opposite, linear induction is not used by Transrapid, only by SCMaglev
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-21T17:38:58Z

0n3!r0!: /* Maglev extensions */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS, the Maglev Track Set, and in one case JP+, which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||V ||Requires onboard supercooling
|-
|V ||VacTrain with synchronous linear motor track ||N/A ||Requires soft vacuum or advanced onboard supercooling
|-
|I ||Maglevs that use a linear induction motor || N/A ||Relies on track power
|-
|v ||VacTrain with linear induction motor track ||N/A ||Requires hard vacuum, relies on track power
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback
|-
|I ||Linear induction motor || D
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme extensions

2025-08-20T22:37:26Z

0n3!r0!: /* Rail System/Gauge [X***] */

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback
|-
|S ||Maglevs that use a synchronous linear motor ||N/A
|-
|I ||Maglevs that use a linear induction motor || N/A
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback
|-
|I ||Linear induction motor || D
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|N ||Narrow gauge (1067mm)
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Roadtype Scheme

2025-08-20T16:23:44Z

0n3!r0!: Added "When to use"/'When NOT to use". No other changes.

This scheme was originally conceived in order to decrease the amount of necessary hidden road and tramtrack types. This is done by standardizing which labels vehicles and infrastructure should use. The standard also allows for more gameplay depth by having the option to limit vehicles to certain types of roads. It does similarly to the railtype scheme allow mixing of any vehicle set with any infrastructure set. It does however not allow multiple infrastructure sets to be used at the same time. It does not prevent it but all of the sets used have to be made to be used with each other, or use different surfaces/types which don't conflict with each other. The standard sets no limit on how vehicle sets can be used.

It is ultimately up to the infrastructure set to chose what roadtypes are available and thereby what vehicles are available. Infrastructure and vehicles can both be in the same set, it is however recommended to be able to disable the infrastructure with parameters (preferably on an individual basis per roadtype) in case the player wants to use a different set for their infrastructure.

== When to use the scheme and when ''not'' to use the scheme ==

When to use:
* If you only want to develop a road type or a vehicle set.
* If you want players to be able to mix-and-match sets.
* If you are okay with abstractions from real life.
* If you are okay with a pool of 63 available roads/tramways.
** You can have a 1:62 or 62:1 ratio or anything in between when using road/tram type slots. They are the same pool.
*** This unfortunately means an average of only 31.5 type slots for roads and another average of 31.5 type slots for tramways.
* If you want to create actual utilization of all 63 road types, for visual and logistical variety.

When ''not'' to use:
* If you consider it a crime against humanity when one of your vehicles or road types is not available in a specific game.
* If your road vehicle set is specifically designed to work with your road set only.
** Caveat: If your road vehicle set is specifically designed to work with any road set that provides the basic requirements, not just your own, it should use the applicable Standardized labels.
* If you just feel the compulsory need to fill all 63 road type slots with variants.

----

=== Surface / Type [X***] ===
Describes the road surface / rail type and thus the vehicle type.

'''Roadtype:'''

{| class="wikitable"
|- style="font-style:italic;"
! Letter
! Meaning (Road)
! Powered Roadtypes
! Recomended vehicle set fallbacks
|-
| R
| Regular Road
| RI(S)
|
|-
| P
| Passenger-only
| RPI(S)
| R
|-
| G
| Guided busway
| RPG
| P then R
|-
| I
| Industrial Site (ISR)
| I
| R
|-
| B
| Bicycle Lane
| RB(Z)
| R
|-
| W
| Waterway
| W
|-
| A
| Amphibious on road (hidden)
| RPI(S)W
| R
|-
| S
| Snowy or Iced Track
| S
|-
| a
| Amphibious on snow (hidden)
| SW
| S
|-
| Z
| Pedestrian Zone
| Z
|
|-
| E
| Eyecandy
| E
|
|-
| p
| Pump/Pipeline
| p
|
|}

'''Tramtype:'''

{| class="wikitable"
|- style="font-style:italic;"
! Letter
! Meaning (Tram)
! Powered Tramtypes
! Recomended vehicle set fallbacks
|-
| R
| Regular Rail
| RI(M)
|
|-
| P
| Passenger-only
| RPI(M)
| R
|-
| I
| Industrial Site (ISR)
| I
| R
|-
| B
| Bicycle Lane
| (R)B
| R
|-
| S
| Suspended Monorail
| S
|
|-
| M
| Metro
| M(RP)
|
|-
| O
| Trackless trams
| O
|
|-
| E
| Eyecandy/Electrical infrastructure
| E
|
|}

It is the vehicle set's responsibility to implement fallbacks to other appropriate surfaces. It is also up to the author to decide if they want to do it or not. This means that road/tramtrack sets shouldn't add these to their [[NML:Roadtypes#Roadtype_properties|alternative_roadtype_list (NML)]] and [[NML:Tramtypes#Tramtype_properties|alternative_tramtype_list (NML)]]

It is up to the track set to implement all powered roadtypes in the [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]]. The same goes for tramtypes: [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]]. It is further advised to implement support for the roadtypes/tramtypes in brackets, if applicable.

Hidden roadtypes for compatibility should be implemented by road sets. It is up to the author to decide if they want to implement it as a hidden roadtype or not.

=== Speed / Feature [*X**] ===
Any character may be used for roads, but at least one road must have "A".

Vehicles should use "A".

=== Terrain / Stability [**X*] ===
Describes the roughness of the road surface / trackbed stability, and thus the vehicle tier.
{| class="wikitable"
|- style="font-style:italic;"
! Letter
! Meaning
! Powered Roadtypes
|-
| a
| Very slow / rough / light
| a
|-
| A
| Slow / rough / light
| aAB
|-
| B
| Regular
| ABC
|-
| C
| Fast / stable
| BCc
|-
| c
| Very fast / stable
| c
|}

If all classes aren't defined by the road set, the other ones should be in the [[NML:Roadtypes#Roadtype_properties|alternative_roadtype_list (NML)]]. The same goes for tramtypes: [[NML:Tramtypes#Tramtype_properties|alternative_tramtype_list (NML)]].

Road vehicle sets should not implement fallbacks for terrain / stability.

Classes "a" and "c" are entirely optional for road/tramtype sets and should under no circumstances be used by vehicles.

=== Energy [***X] ===
Describes the energy source of the track / vehicle.

'''Generic classes:'''
{| class="wikitable"
|- style="font-style:italic;"
! Letter
! Meaning (Road)
! Meaning (Tram)
! Vehicle set fallback
|-
| N
| None
| None
|
|-
| E
| Overhead electrified (Catenary)
| Overhead electrified (Catenary)
|
|-
| G
| Ground electrified
| Ground electrified
|
|-
| Z
| Ground and overhead electrified
| Ground and overhead electrified
| E or G
|}
'''Specialized classes:'''
{| class="wikitable"
|- style="font-style:italic;"
! Letter
! Meaning (Road)
! Meaning (Tram)
! Vehicle set fallback
|-
| 3
| n/a
| Third Rail
| G
|-
| 4
| n/a
| Fourth Rail
| 3 then G
|-
| C
| n/a
| Cable
| G
|}
A tramtrack set that only uses specialized types, should map the generic types to the most suitable specialized type in the set with the help of the [[NML:Tramtypes#Tramtype_properties|alternative_tramtype_list (NML)]].

=== The default labels (ROAD, ELRL) and non-standard labels===
OpenTTD will allways define ROAD and ELRL incase there are vehicles for them. It is therefore recomended to have these present in the set so that you can map them to appropriete labels from the standard. There are a few ways of doing this:
*Replacing one of the standardised types with the default label and putting the standardised label in the [[NML:Roadtypes#Roadtype_properties|alternative_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|alternative_tramtype_list (NML)]].
*Defining ROAD and/or ELRL separately from the standardised labels and adding the standard ones to the [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]]. The main advantage of this is that you can use a parameter to map ROAD and/or ELRL to the standardised labels. This allows the player to chose where there non standardised vehicles will be able to go.

Vehicle set authors might want to add the default labels and non-standard labels as a fallback. If not implemented for the defualt labels, their vehicles won't show up on the default roads and/or tracks, leading to countless bug reports from players. Non standard labels that might be worth adding fallbacks too are: ELRD, RAIL, HAUL and probably some more.

== Summary for Road/Tramtrack sets ==
This section summarizes the above for road/tramtrack sets.

; [X***] Surface / Type
* Chose which Surfaces and types you want in your set and give them the correct [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]].
* If you only provide roads/tramtracks for one surface/type, consider leaving some free road/tramtypes so a player can load an additional set for some other type.
; [*X**] Speed / Feature
* Make sure class A is always available.
* Use B, C and so on if you have multible roads/tramtracks with the otherwise the same label.
; [**X*] Terrain / Stability
* Always define classes A through C for every road/tramtrack surface/type energy combination, either:
** Directly via a real road/tramtype definition;
** Indirectly via the alternate road/tramtype label list, [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]].
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]].
; Default labels [ROAD, ELRL] and non-standard labels
* Always define the default labels when possible, instead of what would be the equivalent of the default label in this scheme.
* Map the equivalent labels from this scheme to the default labels using [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]].
* Map common non-standard labels to the most similar label in this scheme using [[NML:Roadtypes#Roadtype_properties|powered_roadtype_list (NML)]] or [[NML:Tramtypes#Tramtype_properties|powered_tramtype_list (NML)]].

== Summary for vehicle sets ==
This section summarizes the above for vehicle sets.

; [X***] Surface / Type
* Use the surface / type class that matches the vehicle;
* Define a fallback type via the road/tramtype table in case you want the vehicle to be available on a different road or tramtrack if no matching road/tramtrack set is loaded.
** Specialized subtypes like "G" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "P" or "R").
; [*X**] Speed / Feature
* Always use class A for every vehicle.
; [**X*] Terrain / Stability
* Use A, B or C depending on where you want your vehicles to be able to drive.
** A is used for slow offroad capable vehicles which aren't allowed on Motorways and similar Roads
** B is used for vehicles which can drive offroad but are also allowed on Motorways.
** C is used for vehicles which can't go offroad or similar.
** Use B if you aren't sure what to chose.
* Never use a or c.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Default labels [ROAD, ELRL] and non-standard labels
* Define a fallback type to the default labels via the road/tramtype table in case you want the vehicle to be available on the default roads/track if no matching set is loaded.
* Do the same for any non-standard labels that may be relevant.

Be as specific as you want when selecting the road/tramtype, it is the job of the road/track set to select a playable, reduced subset out of all possible type combinations.
=== Example of fallback order for vehicle sets ===
{| class="wikitable"
|- style="font-style:italic;"
! Unchanged label
! Fallback order
|-
| GACE (road)
| GACE -> PACE -> RACE -> (ROAD)
|-
| PAB4 (tram)
| PAB4 -> PAB3 -> PABG -> RAB4 -> RAB3 -> RABG
|-
| IAAG (road)
| IAAG -> RAAG
|-
| AACE (road)
| AACE -> RAAE -> (ELRD)
|-
| RABE (tram)
| RABE -> (ELRL)
|-
| PAAN (tram)
| PAAN -> RAAN -> (RAIL)
|}
== Forum topic ==
Feel free to discuss and ask questions about the scheme at the forum topic [https://www.tt-forums.net/viewtopic.php?t=90715 Here].

Standardized Railtype Scheme extensions

2025-08-20T16:10:46Z

0n3!r0!: Added "Wen to use"/'When NOT to use". I hope this helps?

== When to use the extended scheme and when ''not'' to use the scheme ==

When to use:
* If you want to develop a specialized track and train set with broad compatibility towards other sets.
* If you want players to be able to mix-and-match sets in ways not normally available.
** Mixed voltages and Rack rail are valid reasons.
* If you are okay with abstractions from real life.
** Specifically, this extension page does not have "proper" gauge resolution. All gauges are a range of similar sizes, not an exhaustive list of possibilities.
* If you are okay with complexity in your game.

When ''not'' to use:
* If you want immediate payoff; most if not all these possibilities are barely, if ever, used.
* If you do not want this level of complexity in your mod. It ''is'' optional, the extensions are only for edge cases.
* If you consider it a crime against humanity when one of your vehicles or track types is not available in a specific game.
* If you want your tracks or vehicles to exactly mirror real-life counterparts down to the last mm of gauge width.
* If your train set is specifically designed to work with your track set only.
* If you feel the compulsory need to fill all 64 railtype slots.
** At best, 60 slots are possible. RAIL, ELRL, MONO and MGLV are non-negotiable to the game engine. Additionally, filling all 60 slots with only one track set defeats the purpose of a 60 slot limit; combinatory use.
** If 60 slots are used, the train sets will need to be able to cover the variety. A track set can hypothetically cover all Standardized track use cases, if the intent is that all vehicles will potentially be supported.

==Multi-voltage Trains==
One might be interested in implementing a train which speed and/or power depends on the voltage in the overhead line electrification. In order for this to work properly the newgrf needs to test the track with [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype].

Below is an example from RUKTS code, where a train with a diesel generator has higher speed on high voltage ac tracks. We need to test for only SAAA if it is avaliable, as otherwise we would have the train gain the benefits on all electrified tracks. If it however isn't avaliable we still want to know if the track is electrified which is why we have the second part.

<code>railtype_available("SAAA") ? tile_powers_railtype("SAAA") : (tile_powers_railtype("SAAE") || tile_powers_railtype("ELRL"))</code>

==Rack rail==
There are two different types of rack rail engines, pure rack and rack and adhesion. Pure rack engines may only move on tracks fitted with racks (xRxx) whilst rack and adhesion engines may also move on regular tracks but at a lower tractive effort.

Rack rail is currently implemented in the speed class as a "special type", this is unfurtunate as the speed class would otherwise be trackset private.

===Alternative 1===

====Pure rack engines====
These engines should use *R** as label. A trackset could then prevent these trains from traversing *A** tracks.

====Rack and adhesion engines====
These engines should use *A** as label and test for *R** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. This assumes the trackset will allow *A** on *R**.

====Issues====
*Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.
*French Narrow Gauge Trains Set uses NRAN for rack and adhesion engines so tracksets can not support it as intended and pure rack systems at the same time.

===Alternative 2===

====Pure rack engines====
These engines should use *r** (not in scheme) as label. A trackset would then prevent these trains from traversing *A** tracks but allow them on *R**.

====Rack and adhesion engines====
These engines should use *R** as label and test for *r** using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] or [https://newgrf-specs.tt-wiki.net/wiki/NML:Vehicles#Variables_that_require_an_argument NML tile_powers_railtype]. Tracksets will allow *R** on *A** and *r**.

====Issues====
*Requires more track types than alternative 1.

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Multi-voltage extensions==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Maglev extensions==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback
|-
|S ||Maglevs that use a synchronous linear motor ||N/A
|-
|I ||Maglevs that use a linear induction motor || N/A
|}

==JP+ extensions==
These are extensions to the gauge and energy source type classes currently supported by JP+ tracks and used by JP+ train sets.
===Rail System/Gauge [X***]===
{|
! !!Track type/gauge !!Vehicle set fallback
|-
|s ||Scotch gauge || S
|-
|_ ||Universal || N/A
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Vehicle set fallback
|-
|I ||Linear induction motor || D
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

'''CURRENTLY NOT IMPLEMENTED AND MOSTLY NOT OF VALUE'''

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit/appearance class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The appearance class can be tested for by trains using [https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles#Track-type_test_against_another_track-type_.2863.29 var 63] (which the French Set uses to change vehicle properties on rack rail), but this is generally not standardized, limits interoperability and is only useful for co-developed train and track sets.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-19T21:13:05Z

0n3!r0!: /* Rail System/Gauge [X***] */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), or 16 in (406 mm)]
|-
|2 ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-19T20:29:27Z

0n3!r0!: /* Rail System/Gauge [X***] */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't mind gameplay abstractions but don't want physically impossible combinations (e.g. rail, monorail and maglev cannot have any level crossings with each other). Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-19T20:24:49Z

0n3!r0!: /* Rail System/Gauge [X***] */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge. Use this if you don't care to include pneumatic/atmospheric rail systems. Specifically, this accommodates B (ultrabroad), g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm).
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use if you want to provide a cheaper alternative to X that doesn't support fictional "supertrain" gauges.
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow. Specifically, this accommodates g (2140 mm), V (1600mm), S (1435 mm), and R (1000 mm). Use with minus (<nowiki>-</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow. Specifically, this accommodates V (1600mm), S (1435 mm), R (1000 mm), and n (600 mm). Use with plus (<nowiki>+</nowiki>) if you want to give a bit of a puzzle to players over how to design a network limited by a "one or the other" pair of railtypes.
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T21:09:35Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T21:08:43Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a train set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T21:07:53Z

0n3!r0!: /* Axle load class [**X*] */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T21:07:35Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T21:04:54Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||23 metric tonnes (23000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight "FLEXX Eco" and "FLEXX Eco Commuter" bogies ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001 (FLEXX Eco)
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean "DYNAFREIGHT" and "FLEXX Eco Regional" bogies ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|2016 (FLEXX Eco, Regional var.)
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T20:03:36Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight bogies ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|2001
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|2016
|-
|E ||Very High ||40 metric tonnes (40000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T19:58:50Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any **D* tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight bogies ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|2001
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|2016
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T19:57:35Z

0n3!r0!: /* Axle Loads by Real World Implementation */

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. It assumes that, in lieu of a track set that has ever implemented "d" as an axle weight, that instead "4" be used and a "3" placed between C and D for similar reasons. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1910
|-
|3 ||Medium, lightweight bogies ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|2001
|-
|D ||High ||31 metric tonnes (31000kg) per axle || style="text-align:right;"|~1930
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|2016
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-18T19:51:09Z

0n3!r0!:

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

====Axle Loads by Real World Implementation====
The table below is compatible with those above but functions differently than the ones above. All the same classes are listed, however axle weight guidelines have been run by a research LLM which suggested different ranges of weight and different dates of availability. 4 is identical to d in practice. If "d" is not defined as a lighter axle weight than "c", then **4* should be used alongside it in an alternative_tracktype_list for any **D** track type with axle weight "D". If "d" is defined as a lighter axle weight than "c", only tracktypes with axle weight "4" (**4*) should be listed in the alternative_tracktype list for any tracktype.

Use **4* on all applicable rolling stock going forward, and rely on track sets to define "d" for vehicle sets.

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||5 metric tonnes (5000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||10 metric tonnes (10000kg) per axle; Because reserved by examples || style="text-align:right;"|~1820 (Early rail focused on carrying capacity over speed)
|-
|A ||Very Low (2012 OG Default)||15 metric tonnes (15000kg) per axle || style="text-align:right;"|~1870
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|~1890
|-
|C ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|~1930
|-
|3 ||Medium ||26 metric tonnes (26000kg) per axle || style="text-align:right;"|2001
|-
|D ||High ||31 metric tonnes (30000kg) per axle || style="text-align:right;"|1988
|-
|4 (Formerly d) ||High, extra-lean freight bogies ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|2016
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|1988
|-
|F ||Fortescue/Future-proofed ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|2008
|}

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E||
|-
|z ||Atypical catenary voltage ||U, then E
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}

Standardized Railtype Scheme

2025-04-15T00:08:13Z

0n3!r0!: I think it's weird these were never put on this list, it has so many other obscure systems

This railtype label scheme aims to bring order to the uncontrolled growth of railtype labels. It groups the rail types into what matters from a technical perspective. The scheme provides a standardized way of defining railtype labels, based on track gauge and type, speed class, allowable axle weight and electrification type.

It is the explicit intent of this scheme to decouple track sets from vehicle sets to facilitate easy mixing. This way the player can select a track set of choice to go with a train set of choice. It allows the player to play with or without axle load classes, or with or without speed limit classes, simply by loading a track set that does or does not provide these features. In some cases it will also be possible to combine niche track sets, for instance a standard gauge track set with a narrow gauge and a metro track set.

== The Label Scheme ==
A railtype label consists of four characters. In this scheme, each position has a different purpose:
# Track gauge and type class (e.g. standard gauge rail, narrow gauge rail, monorail)
# Speed limit class
# Axle load class (maximum allowed axle weight for this track)
# Energy source type class

In the next sections, each of the four positions will be explained.

=== Track gauge and type class [X***] ===
The first position in the railtype label defines track gauge and/or track type class. The following classes are currently defined:

{|
! !!Track type/gauge
|-
|S ||Standard gauge rail
|-
|B ||Broad gauge rail
|-
|N ||Narrow gauge rail
|-
|n ||Secondary narrow gauge rail (e.g. when providing both metre and cape gauge, always use N in case of just one type of narrow gauge)
|-
|D ||Dual gauge rail, standard/broad gauge
|-
|d ||Dual gauge rail, standard/narrow gauge
|-
|M ||Monorail
|-
|L ||Magnetic Levitation
|}

=== Speed limit class [*X**] ===
The second position in the railtype label defines the speed limit class. These classes do not map to a fixed numeric value, but are used to define an internal speed limit order for the track set. This means that if your track set has two different speed limits for track types that are otherwise identical, you'll use letters A and B here. In case of three different speed limits, use A, B and C. In case your track set does not employ speed limits, always use A. Train sets do not care about the speed limit, and will always set the lowest speed class, i.e. A.

This gives for instance the following options:

<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||no speed limits
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||high speed
|}
</div>
<div style="float:left;">
 OR 
</div>
</div>
<div style="float:left;">
<div style="float:left;">
{|
! !!Speed limit class
|-
|A ||low speed
|-
|B ||medium speed
|-
|C ||high speed
|}
</div>
<div style="float:left;">
 etc. 
</div>
</div>
<div style="clear:left;"></div>

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|R ||rack rail, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|S ||subterranean ||eyecandy ||Metro Track Set
|-
|U ||urban ||eyecandy ||Metro Track Set
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack-rail set) implements compatibility both ways which makes pure rack systems impossible.

=== Axle load class [**X*] ===
The third position defines the axle weight limit. Heavy trains cannot run on tracks with a low axle weight limit; these trains need more expensive tracks with a heigher weight limit. There are five axle load classes '''A''' through '''E'''. '''A''' is for the lowest axle load limit, '''E''' for the highest. The exact axle load attached to each class is relative to the track gauge/type and trains in the set.

A train set should set the appropriate axle weight for each train via the railtype label, as to make the set work with track sets that do provide tracks with different weight limits, even if you don't care about it for your trainset. Split all vehicles of a certain track gauge/type into five groups of similar axle weight. The group with the lowest axle weights will get class '''A''', the second lowest class '''B''', etc. up to the group with the highest axle weights which will get class '''E'''. Do the same for the other track gauge/types if your train set has those.

A track set does not have to provide a dedicated track type for each axle weight limit. A track set that does not provide a dedicated track for each axle load class, must make sure to map all undefined axle load classes to a real railtype using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]]. This way a train set can rely on all labels for all axle load classes being available. Example: if you only want to provide 2 axle load classes for standard gauge unelectrified with no speed limits, you can map SA'''A'''N + SA'''B'''N to SA'''C'''N and SA'''D'''N to SA'''E'''N if the cost difference between the two railtypes is high, or SA'''A'''N to SA'''B'''N and SA'''C'''N + SA'''D'''N to SA'''E'''N if the cost difference is low.

If you don't want to provide any axle load classes in your track set, it doesn't really matter what axle load class you choose for the track, as you'll be mapping all other classes to this track anyways. But the lowest or highest class are the obvious choice. Example: if your track set only provides narrow gauge unelectrified track with no speed limits and no axle load limits, you may use NA'''A'''N for the track label, and provide NA'''B'''N, NA'''C'''N, NA'''D'''N, NA'''E'''N in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

If you need more than five axle load class, you may use lowercase letters for very low axle loads and continue the uppercase letters for very high axle loads. Be advised that your train set may not assume the existance of any other class than '''A''' through '''E''', so when the range make sure to program your railtype table such that trains with such a class will fall back to class '''A''' or '''E'''. If you make a track set with an extended range, be aware that not all train sets will define trains for these tracks. In general: only do this in case of a train set with a matching track set.

For the lowercase letters, '''b''' is lower than '''a''', so for increasing axle load limits: b < a < A < B < C etc.

Note that the axle load classes never map to a specific weight in tonnes. For that reason it does not make sense to add a numeric value for the axle load to the name of a track type or in the extended purchase info of a train. Instead use the relative expressions 'very low', 'low', 'medium', 'high' and 'very high' or use the class letters directly.

If a guideline is needed for updating a set to use axle loads in a train set where they don't yet exist, the following might serve as a basic "generic" guideline...

{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|F ||Future-proofing ||No limit per axle (update in 2030 or so?) || style="text-align:right;"|~2028
|}

=== Energy source type class [***X] ===
The last position defines the energy source type class. This is split in generic energy source types like overhead wires and third rail and specialized types like alternating and direct current.

A track set that only uses specialized types, should map the generic types to the most suitable specialized type in the set.

A vehicle set that uses specialized types should define a generic type as fallback, via the railtype table. If such a fallback is omitted, please note that certain vehicles may be unavailable depending on track set loaded.

{|
! !!Generic energy type classes
|-
|N ||no electrification
|-
|E ||overhead wires/catenary electrification
|-
|3 ||3rd rail electrification
|}

{|
! !!Specialized energy type classes !!Vehicle set fallback
|-
|Z ||3rd rail and catenary electrification || 3 or E
|-
|4 ||4th rail electrification || 3
|-
|Y ||4th rail and catenary electrification || 4 or E
|-
|T ||[http://en.wikipedia.org/wiki/Three-phase_AC_railway_electrification three phase AC electrification] || E
|-
| colspan="3" |  
|-
|D ||DC catenary electrification || E
|-
|d ||low voltage DC catenary electrification (only when D also used in set) || First A then E
|-
|A ||AC catenary electrification || E
|-
|a ||low voltage AC catenary electrification (only when A also used in set) || First A then E
|}

If you want multi-voltage/current vehicles in your set (i.e. a train that can run on both AC and DC current), you have to define a dedicated railtype for those vehicles. Without the railtype, it's not possible to define vehicles with this property. If you only have vehicles that can run on either one type of voltage/current or on all types of voltage/current (e.g. a 2-system if you only have '''A''' and '''D''' tracks, or a 4-system in case of all '''A''', '''a''', '''D''' and '''d'''), then use the generic class '''E''' for vehicles that should be able to run on all different voltage/currents. Also the track set needs to have one at least one railtype with class '''E''' defined.

Note that if you want more than one type of multi-voltage/current, you'll quickly get a combinatory explosion of railtype labels, so plan carefully or do not attempt it. For every different multi-voltage/current vehicle type a dedicated railtype is needed. If you want all possible combinations, then you need to define an additional 8 classes. It is not recommended to make your train/track set this complicated.

Example approach for a 4-system set, with trains that can run on either one or all systems:
* '''E''': generic catenary-powered electric engines. "universal" [4-system] if any of '''D'''/'''d'''/'''A'''/'''a''' are defined.
* '''A''': generic AC catenary electric engines. 25kV only if '''a''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''A''';
* '''a''': 15kV AC catenary electric engines. Only defined if '''A''' also defined. Vehicle sets should use '''A''' and '''E''' as fallback, if defining an engine for '''a''';
* '''D''': generic DC catenary electric engines. 3kV if '''d''' also defined. Vehicle sets should use '''E''' as fallback, if defining an engine for '''D''';
* '''d''': 1.5kV DC catenary electric engines. Only defined if '''D''' also defined. Vehicle sets should use '''D''' and '''E''' as fallback, if defining an engine for '''d'''.
For a 2-system set, you can simply drop '''a''' and '''d'''.

=== Standard labels: RAIL, ELRL, MONO, MGLV ===
It's not possible to undefine the standard railtypes RAIL, ELRL, MONO and MGLV. The game will always add those if there are vehicles defined for these track types. As a result, for a track set it's best not to ignore those standard labels, but rather work with them and define them in the set. If your track set does not have monorail or maglev tracks, there of course is no need to define those. But if your track set defines anything that resembles unelectrified or electrified rail, you should use the RAIL and ELRL labels. Matching labels from the above scheme will then be defined in property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

As vehicles from NewGRFs that do not use explicit railtypes will end up on these standard railtypes, you should use RAIL instead of whatever type could be regarded as the most commonly used unelectrified type, ELRL instead of the most commonly used electrified type and so on. The label according to this scheme is then set as an alternate.

== Summary for track sets ==
This section summarizes the above for track sets.

; [X***] Track gauge and type class
* Define at least one track type for every track gauge/type class you want in your set.
* If you only provide tracks for one gauge/type, consider leaving some free railtypes so a player can load an additional set for some other type.
; [*X**] Speed limit class
* Make sure class A is always available, either directly or via an alternate label.
* Use only class A if you don't want speed limits;
* With speed limits, A is the lowest speed limit. Continue with B, C, etc. for increasing speed limits;
* The speed class can also be used to implement additional eye-candy track types, use letters higher in the alphabet for this.
; [**X*] Axle load class
* Always define all classes A through E for every track type class / electrification combination, either:
** Directly via a real railtype definition;
** Indirectly via the alternate rail type label list, property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].
* Extend the predefined classes only if you also provide a train set that makes use of these.
; [***X] Energy source type class
* If your set only uses specialized classes, always map the generic classes to the closest matching specialized type via property 1D.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Always define the standard labels when possible, instead of what would be the equivalent of the standard label in this scheme.
* Map the equivalent labels from this scheme to the standard labels using property [[Action0/Railtypes#Alternate_rail_type_labels_.281D.29|1D (NFO)]] or [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]].

Or, put differently, for each gauge/type, select one or more energy source types. For each type/energy combination provide all axle load classes for the speed class "A", either as a real type or as an alternate of another type. Provide more types with a different speed letter if you want to provide several different speeds or other eye-candy tracks.

== Summary for train sets ==
This section summarizes the above for train sets.

; [X***] Track gauge and type class
* Use the track type class that matches the vehicle;
* Define a fallback type via the railtype table in case you want the vehicle to be available on a different track if no matching track set is loaded.
** Specialized subtypes like "n" might not always be available. If you want those vehicles to be still available then, fall back the the generic class (e.g. "N").
; [*X**] Speed limit class
* Always use class A for every vehicle.
; [**X*] Axle load class
* Use all classes A through E according to the maximum axle weight of the vehicle.
* Extend the predefined classes only if you also provide a track set that makes use of these;
** When extending the predefined classes A through E, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; [***X] Energy source type class
* Use the energy source type class that matches the vehicle;
* When using specialized classes, define a fallback type via the railtype table in case you want the vehicle to be available if no matching track set is loaded.
; Standard labels [RAIL, ELRL, MONO, MGLV]
* Define a fallback type to the standard labels via the railtype table in case you want the vehicle to be available on the standard tracks if no matching track set is loaded.

Be as specific as you want when selecting the railtype, it is the job of the track set to select a playable, reduced subset out of all possible type combinations.

== In case you're not convinced by this scheme ==
Adopting this scheme gives the player freedom to use any track set in combination with any train set that follow the scheme.

This means that you can make your train set compatible with track sets that provide axle load classes, and track sets that provide speed limits, and at the same time with track sets that provide none of this. This way, the player can decide to play with or without axle load classes, or with or without speed limits, simply by loading a track set that does or does not provide these features.

And for your track set, it means that you can make it as simple or as complicated as you want (within the 64 track type limit), while not having to worry about compatibility with train sets.

Still not convinced? Feel free to use railtype labels of your own, but know that you will likely come to regret that at some point in the future.

==Forum topic==
If you want to discuss the standardized railtype scheme or have any questions about it, you can visit [http://www.tt-forums.net/viewtopic.php?t=59379 the forum topic].

=="Innsbruck 2022 Convention" for partial compliance==

This is really esoteric, but eh. It was the product of long discussion / debate / argument / reasoning between grf authors.

1. The Standardized Railtype Scheme '''is a useful tool''' for providing reliable compatibility between train grfs and railtype grfs.

2. The '''axle load class''' in the scheme presents a number of issues for compliance.

2.1. Over 10 years since the scheme was standardised, not many train grfs implement multiple axle load classes '''as required by the scheme'''. Known examples that '''do''' comply include Dutch Train Set, French Narrow Gauge Trains, and Finnish Trains.

2.2. Elements of the axle load rules have proven hard to interpret. For example:

* is it compliant to use ''fewer'' than 5 classes in a train grf? There is a lack of consensus on this.
* axle load is only one of many factors that govern whether a vehicle is compatible with a route, for example loading gauge, minimum curve, signalling types etc

2.3. Meanwhile ''multiple existing train grfs use class ''A'' for the axle load for all trains'' (except where relying on default railtypes such as RAIL and ELRL).

'''3. The Innsbruck 2022 Convention uses class ''A'' for axle load for '''all''' trains in a train grf (except where relying on default railtypes such as RAIL and ELRL).'''

This is '''not''' fully compliant with the Standardized Railtype Scheme and does not claim to be.

However train grfs using the Innsbruck 2022 Convention are ''broadly compatible'' with railtype grfs using the Standardized Railtype Scheme.

Obligatory XKCD link about 'standards': https://xkcd.com/927/

===Known issues===

Known problems are that trains using only class 'A' may limit the ability of railtype grf authors to achieve their design goals for separating railtypes by axle load.
But on reflection, it can be seen that a train grf might not be able to provide a broad enough range of vehicles to cover at least 5 axle load classes.

3.1. The Innsbruck 2022 Convention is '''not''' appropriate for train grf authors who wish to provide more than one axle load class.

3.2. The Innsbruck 2022 Convention treats the meaning of class ''A'' as ''undefined'', ''ignored'' or ''compatible with most restricted railtype'' for axle load.

Axle load class ''A'' '''cannot''' be safely interpreted as ''universal'' because from the perspective of a railtype grf ''A'' is ''most restricted railtype'', where ''universal'' is better represented as ''least restricted railtype''. Depending how many axle load classes are in use by the railtype grf, this could be class ''B'', ''C'', ''D'', ''E'' etc. To illustrate this issue, take the following scenario

* railtype grf defines axle loads ''A'' to ''E''. In this case the railtype grf author intends that ''A'' is compatible with the smallest range of vehicles, ''E'' is compatible with the largest range of vehicles, and ''B'', ''C'' and ''D'' are compatible with some intermediate ranges of vehicles
* but the vehicle grf author has defined all vehicles to be axle load ''A'' in an attempt to express this vehicle is ''universal''. The result in the game is that an identical range of vehicles will be compatible with railtypes ''A'' to ''E''.

This is clearly '''not''' the intended outcome of the railtype author. But nor is it clear within the spec that the vehicle author has particularly done anything wrong.

It ''would'' be possible to use railtype availability testing to adjust the vehicle property 05 (track_type) to fit the highest defined axle load (''E'' in this example case), but this is not insignificant work, and it's unlikely to be widely adopted by vehicle grf authors. Nor would this solution achieve ''universal'' as all vehicles in vehicle grf then would be incompatible with types ''A'' through ''D''.

3.3. When the Innsbruck 2022 Convention is used, this '''does not prevent''' a train grf being extended in some future release to achieve full compliance with Standardized Railtype Scheme. ''That choice remains with train grf authors''.

3.4. If 2012 could be revisited, providing an optional ''_'' axle load class in the Standardized Railtype Scheme for ''undefined'' would have been preferable, but as of 2022, ''A'' is already widely used for this purpose, and time travel is not known to be possible.

==Extended multivoltage support addition==
These are extensions to the energy source type class currently supported by SETS and xUSSR Rails which allow trainsets to code trains which are limited to a certain selection of voltages. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for trainsets for ideal functionality with tracksets which support the extended labels.
{|
! colspan="2" | Specialized energy type classes !!Vehicle set fallback
|-
|* ||Equivilent to A, a, D and d || E
|-
| colspan="3" |  
|-
|' ||Equivilent to A, a and D || E
|-
|^ ||Equivilent to A, a and d || E
|-
|_ ||Equivilent to A, D and d || E
|-
|, ||Equivilent to a, D and d || E
|-
| colspan="3" |  
|-
|$ ||Equivilent to A and a || First A then E or just E
|-
|= ||Equivilent to D and d || First D then E or just E
|-
|) ||Equivilent to A and D || E
|-
|( ||Equivilent to A and d || E
|-
|] ||Equivilent to a and D || E
|-
|[ ||Equivilent to a and d || E
|}

==Extended maglev support addition==
These are extensions to the rail system and energy source type classes currently supported by RIMS, FRIMS and the Maglev Track Set which allow trainsets to code trains which use different, incompatible maglev variations. As stated in the energy source type class section this might not be of use for all sets, as such it is optional but still recommended for all maglevs in trainsets for ideal functionality with tracksets which support the extended labels.

===Rail System/Gauge [X***]===
{|
! !!Track type/gauge
|-
|L ||Maglevs that have a u-shaped track (SCMaglev)
|-
|T ||Maglevs that have a monorail track (Transrapid/China)
|}

=== Energy source type class [***X] ===
{|
! !!Electrification !!Fallback !!Notes
|-
|S ||Maglevs that use a synchronous linear motor ||N/A ||
|-
|I ||Maglevs that use a linear induction motor || TCAI (the whole label) || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback.
|-
|V ||Vactrains/Hyperloop ||t, then I || If using SCMaglev/"Vanilla" maglev then add MGLV (the whole label) as an extra fallback. See proposed "universal tunnel" electrification below for the "t".
|}

==Possible additions==

There are a number of proposed labels for standardization of non-standardized labels...

===Rail System/Gauge [X***]===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Track type/gauge
|-
|_ ||Universal "cheat" rail; ALWAYS add "_H_c" and "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|compatible_railtype_list (NML)]], and ALWAYS add "_S_t" to EVERY [[NML:Railtypes#Railtype_properties|powered_railtype_list (NML)]] if you intend to support this
|-
|0 ||(A number zero, not a letter "Oh") No track, eyecandy-use only
|-
|U ||[https://perma.cc/93VE-8JQZ "Ukrainian monorail" or Şaropoí̈zd (Шаропоїзд)], a u-shaped concrete "monorail trench" from 1920's Soviet Union; see [https://www.tt-forums.net/viewtopic.php?f=26&t=47432 the Yarmanchuk Express] for graphics
|-
|1 ||Early Monorail; See [https://perma.cc/6BVS-2P2X here] and [https://perma.cc/VCG2-ATUA here]
|-
|G ||Gyrail; [https://en.wikipedia.org/wiki/Gyro_monorail Gyro monorail/Gyroscopic monorail/Gyro-stabilized monorail] for description and IRL example, and [https://wikimon.net/Trailmon here] ([https://web.archive.org/web/20240227205547/https://wikimon.net/Trailmon archived]) for good fictional examples
|-
|A ||Alweg-based Monorail
|-
|m ||Minimum gauge rail; [https://en.wikipedia.org/wiki/Minimum-gauge_railway 15 in (381 mm), 400 mm (15+3⁄4 in), 16 in (406 mm), 18 in (457 mm), 19 in (483 mm), 500 mm (19+3⁄4 in) or 20 in (508 mm)]
|-
|n ||600mm "Decauville" or "Feldsbahn", formerly labelled "NG60" before standardization; the most common narrow gauge track type in OpenTTD other than metre gauge, 600mm gauge is thus ideal for taking up the "n" gauge, though this is an ultimately optional distinction
|-
|7 ||750mm, Bosnian gauge (760 mm), and 762mm; all start with 7 and are close in size
|-
|3 ||Swedish 3 foot (891 mm), 900mm, 3 foot (914 mm) and Italian Metre (950mm) gauges
|-
|R ||Metre gauge; potentially compatible with base tramtype "RABN", most early tramways were metre gauge
|-
|4 ||4 foot gauge (1219 mm), and possibly 4'6" in. (1372 mm) if standardization is needed for 1372mm
|-
|s ||Scotch gauge (1372 mm)
|-
|S ||Standard gauge; already implemented in original standardized railtype scheme, but could include near-standard (1422+ mm) as well as existing true standard (1435 mm) and is also potentially compatible with the SAbN tramtype
|-
|X ||Omni-gauge rail (for at-grade multi-gauge crossings and stations); ultrabroad/secondary broad/primary broad/standard/primary narrow/secondary narrow gauge
|-
|x ||Multi-gauge rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow/secondary narrow
|-
|<nowiki>+</nowiki> ||Quad-gauge (Four-gauge) rail (for at-grade multi-gauge crossings and stations); secondary broad/primary broad/standard/primary narrow
|-
|<nowiki>-</nowiki> ||Four-gauge rail (for at-grade multi-gauge crossings and stations); primary broad/standard/primary narrow/secondary narrow
|-
|b ||Broad gauge rail - As broad gauge is a rare tracktype, it may still be feasible to cement B and b as broad gauges of two differing sizes, but the rarity among gauges in the real world would need to match; Italian (1445 mm), Dresden (1450 mm) and Leipzig (1458 mm) gauges are all based on streetcar/tram systems and may be better grouped here
|-
|t ||Greater Toronto Area streetcars (1495 mm)
|-
|5 ||1520mm and 5 foot (1524 mm) gauges
|-
|V ||Pennsylvanian (1581 mm and 1588 mm) and Australian "Victorian" (1600 mm) gauges
|-
|6 ||6 foot (1829 mm) broad gauge
|-
|g ||Brunel's Great Western Railway gauge (2140 mm)
|-
|B ||Biggest Broad gauge rail - As broad gauge is a rare tracktype, and the variation in common real life track types too wide, it may be desirable to cement B and b as broad gauges of two differing sizes; With no real life examples that match the usage frequency of "B", the gauge might best draw inspiration from the infamous [https://en.wikipedia.org/wiki/Breitspurbahn Breitspurbahn] (3000 mm) and [https://perma.cc/KQ2Z-5RCR the never-built vehicles designed for it], or from the [https://en.wikipedia.org/wiki/Brighton_and_Rottingdean_Seashore_Electric_Railway Brighton & Rottingdean Seashore Electric Railway] (18 ft/5,486 mm)
|-
|F ||Flightrail; A [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ system capable of high speeds and steep hill grades] that uses a pneumatic pipe for propulsion (see "P" under energy sources), and ''wheels pointed inwards at a 45-degree angle''
|}

It might be preferred to instead use/keep "B" for "all (current) broad gauges" (mostly Victorian gauge) instead using lowercase "b" for Brunel/GWR broad gauge. This wouldn't be to different from narrow gauge since the lesser used ones are lowercase and fallback to the uppercase ones.

=== Speed limit class [*X**] ===

The speed limit class may also be used for some advanced features of the label scheme, like specialized track types and eyecandy purposes. Be careful not to break the compatibility with other sets when using the speed limit class for these purposes.

An example of a special use is rack rail. In the French set it is used to give rack rail engines a higher speed and TE than normal rail engines when used on rack rail. When defining trains with a special speed limit class, always allow a fallback to speed limit class A via the railtype table.

An example of eyecandy use are urban tracks. These are a variation of regular tracks, but with concrete ground tiles to better match the urban environment. Train sets must not define vehicles for eyecandy classes. If you think you have special vehicles that should only run on the eyecandy class, it is ''not'' eyecandy but a separate track gauge/type.

The following special and eyecandy classes have been defined so far:

{|
! !!Description !!Type !!Used by
|-
|A-H ||speed limits ||colspan="2"| reserved
|-
|K-R ||rack rail with speed limits, that allows rack-equipped vehicle to not slow down going uphill ||special ||French Set Rails
|-
|k-r ||rack rail with speed limits, that powers a rack-only vehicle ||special ||
|-
|s ||subterranean (low-clearance) ||eyecandy, should not be supported by double-deck passenger carriages or double-stack container wagons ||
|}
Rack rail needs a bit greater of a explanation, ideally it would be coded in a way where both pure rack and rack-and-adhesion systems are supported.
This can be achieved by making regular tracks powered on rackrail without the opposite being true. This means vehicles defined for NRAN can't go on NAAN (like a pure rack system) but NAAN vehicles can go on NRAN (like a rack-and-adhesion system). Currently French Set Rails (the most popular rack set) implements compatibility both ways which makes pure rack systems impossible.

Should another rack rail set be implemented, it might be prudent to make K-R equivalent to A-H for rack-and-adhesion, and k-r equivalent to A-H for rack rail only.

=== Axle load class [**X*] ===
{| class="mw-collapsible mw-collapsed"
! !!Indefinite !!Generic !! First usage
|-
|c ||Horse-drawn Wagonway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1594
|-
|b ||Iron Plateway ||1 metric tonne (1000kg) per axle || style="text-align:right;"|1799
|-
|a ||Prototype Rails ||5 metric tonnes (5000kg) per axle; Because reserved by examples || style="text-align:right;"|1820
|-
|A ||Very Low (2012 OG Default)||10 metric tonnes (10000kg) per axle || style="text-align:right;"|1828
|-
|B ||Low (2024 "New" Default) ||20 metric tonnes (20000kg) per axle || style="text-align:right;"|1968
|-
|C ||Medium ||30 metric tonnes (30000kg) per axle || style="text-align:right;"|~1978
|-
|D ||High ||40 metric tonnes (40000kg) per axle || style="text-align:right;"|1988
|-
|d ||High, extra-lean freight bogies ||50 metric tonnes (50000kg) per axle || style="text-align:right;"|2008
|-
|E ||Very High ||50 metric tonnes (50000kg) per axle (update in 2030 or so?)|| style="text-align:right;"|~2028
|-
|F ||Future-proofing ||No limit per axle (update in 2050 or so?) || style="text-align:right;"|~2048
|}

If the above scheme is used, "d" should NEVER be used as the axle weight of a railtype. Instead, if your train set supports axle weights, use SAdN/SAdE/etc. as a vehicle's axle weight if they are a freight car available between 2008 and 2028 but are more than 40 metric tonnes (40000kg) per axle, and add the railtype to the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of SADN or equivalent.

=== Energy source type class [***X] ===
{| class="mw-collapsible mw-collapsed wikitable"
! !!Electrification !!Fallback !!Notes
|-
|1 ||Unspecified monorail electrification |||MONO (the whole label) ||
|-
|t ||"Universal custom tunnel" (for diagonal sub-surface "rail tunnels" that use decorative track types to complete the illusion) ||c, then p, then 7, then U (mandatory) ||
|-
|<nowiki>-</nowiki> ||Universal energy type (''not'' meant to replace "***N"; use for vehicles such as driving cabs which cannot move under their own power regardless, if desired) ||N/A (Be sure to put "***E" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***-" label) ||(''Do not give a fallback or use for railtypes, this is for unpowered "locomotives" only!'')
|-
|5 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3") and 630v DC Inner 3rd/4th Rail; a total of 5 rails (2 for wheels, 3 for electricity), plausible in the London Underground network ||3 or 4 ||
|-
|U ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail and universal catenary (SAEE); a total of 5 rails (2 for wheels, 3 for electricity) if only one gauge, plausible in the London Underground network and an "ultimate" dual rail electrification without being a cheat (make it expensive or toggle-able?) as SAEU or as XAEU (universal dual rail electrified tracks) ||E ||
|-
|7 ||750v DC Outer 3rd Rail ("MTRO" or "SA_3"), 630v DC Inner 3rd/4th Rail, Three-phase AC (SA_T) 3rd/4th rail & catenary, and universal catenary (SA_E); a total of 7 rails (2 for wheels, 5 for electricity) if only one gauge, a truly universal dual rail electrification without being impossible (make it VERY expensive or toggle-able so it isn't cheat-y?) as SAE7, XAE7 or even as XRE7 (combination of ALL two-rail track gauges with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible) ||U ||
|-
|<nowiki>+</nowiki> ||750v DC catenary ||U, then E ||
|-
|6 ||600v DC catenary ||U, then E ||
|-
|P ||Pneumatic tube with physical piston slit, or closed pneumatic tube with magnetic piston (i.e. that used by [https://web.archive.org/web/20231213122530/http://www.flightrail.com/ Flightrail]) ||N/A ||
|-
|p ||Pneumatic and universal electrical power ||P or 7 (Be sure to put "***_" and ***P" in the [[NML:Railtypes#Railtype_properties|alternative_railtype_list (NML)]] of a "***p" label) || XREp is a combination of ALL two-rail track gauges with improbably high axle load with universally-compatible electrification including an outer 3rd rail and a paired set of inner 3rd/4th rails, and a rack rail in the exact center; improbable, but not physically impossible)
|-
|c ||Cheat electrification type; use solely for the "_R_c" and "_R_t" railtype labels specifically (runs everything if coded properly), the latter ("_R_t") is for tunnels, while the former ("_R_c") is for "cheat rail upgrade" newgrfs ||p, then 7, then U, then E, then N, then "SA_-" (the whole label) ||
|}