Standardized Roadtype Scheme

This scheme was originally conceived in order to decrease the amount of neccesary hidden road and tramtrack types. This is done by standardising 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 multible 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 diffrent 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 avaliable and thereby what vehicles are avaliable. Infrastructure and vehicles can both be in the same set, it is however recommended to be able to dissable the infrastructure with parameters in case the player wants to use a different set for their infrastucture.

Surface / Type [X***]

Describes the road surface / rail type and thus the vehicle type.

Roadtype:

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:

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
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 alternative_roadtype_list (NML) and alternative_tramtype_list (NML)

It is up to the track set to implement all powered roadtypes in the powered_roadtype_list (NML). The same goes for tramtypes: 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.

Letter	Meaning	Powered Roadtypes
a	Very slow / rough / light	aA
A	Slow / rough / light	aAB
B	Regular	ABC
C	Fast / stable	BCc
c	Very fast / stable	Cc

If all classes aren't defined by the road set, the other ones should be in the alternative_roadtype_list (NML). The same goes for tramtypes: 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:

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:

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 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 alternative_roadtype_list (NML) or alternative_tramtype_list (NML).
• Defining ROAD and/or ELRL separately from the standardised labels and adding the standard ones to the powered_roadtype_list (NML) or 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 powered_roadtype_list (NML) or 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, powered_roadtype_list (NML) or 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 powered_roadtype_list (NML) or 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 powered_roadtype_list (NML) or powered_tramtype_list (NML).
• Map common non-standard labels to the most similar label in this scheme using powered_roadtype_list (NML) or 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

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 Here.

Possible additions

To be discussed in the forum topic...

Surface / Type [X***]

Describes the road surface / rail type and thus the vehicle type.

Tramtype:

Letter	Meaning (Tram)	Powered Tramtypes	Recomended vehicle set fallbacks
X or x	Multiple guidance systems or guages	(Depends on intent; only two tramtype rail system combinations can exist for a given set of standardized labels - i.e. XABE and xABE - making it necessary to plan accordingly)

Energy [***X]

Describes the energy source of the track / vehicle.

Generic classes:

Letter	Meaning (Road)	Meaning (Tram)	Vehicle set fallback
i	Eyecandy/Pipeline Infrastructure	Eyecandy/Electric & Telecom Infrastructure	N/A

Specialized classes:

Letter	Meaning (Road)	Meaning (Tram)	Vehicle set fallback
x	N/A	Unelectrified, Multiple Systems	For use when a standardized tramtype (such as tram rails) label (RABN) with no catenary graphics and one or more specialized, non-compatible tramtype with catenary (such as suspended monorail and pneumatic subway) label (MONO, VACT) overlap
X	N/A	Electrified, Multiple Systems	For use when the default label (ELRL) or a standardized tramtype label (RABE, etc.) with catenary graphics and one or more specialized, non-compatible tramtype with catenary (such as suspended monorail and pneumatic subway) label (MONO, VACT) overlap