{{NMLNavBlocksyntax}}
Sort block allows arbitrary sorting of vehicles.

sort(<feature>, [<ID>, <ID>, <ID>...]);

The engines will be sorted in the given order on the position where originally the first element was. Say the original engine sorting is this: A B C D E and you use this code <code style="color:darkgreen">sort(FEAT_TRAINS, [D, B, A]);</code> the final sorting will be this: C D B A E

2013-05-15T11:43:30Z

Juzza1:

{{NMLNavExpressions}}

Available builtin functions are

{| class="t"
! Function
! Description
|-
| min(''v1'', ''v2'')
| Return the smallest value
|-
| max(''v1'', ''v2'')
| Return the biggest value
|-
| date(''year'', ''month'', ''day'')
| If all values are constants, returns the number of days since year 0. If the year is a variable, the month and day should be 1.
|-
| day_of_year(''month'', ''day'')
| Return the day of the year since January 1st. Both values must be compile-time constants.
|-
| bitmask(''bitpos1'', ...)
| Compose an integer by switching the bits at the given positions on.
|-
| STORE_TEMP(''value'', ''address'')
| Store value in temporary storage
|-
| STORE_PERM(''value'', ''address'')
| Store value in permanent storage (industries, airports, towns only). Note that accessing permanent town registers thrashes the contents of temporary register 0x100.
|-
| LOAD_TEMP(''address'')
| Get value from temporary storage
|-
| LOAD_PERM(''address [, grfid]'')
| Get value from permanent storage (industries, airports, towns only). For towns only, specifying a grfid (4-byte string, optional) allows reading the storage of other grfs. Note that accessing permanent town registers thrashes the contents of temporary register 0x100.
|-
| hasbit(''value'', ''bit_num'')
| Test whether a bit in a value is on
|-
| version_openttd(''major'', ''minor'', ''revision''[, ''build''])
| Return the constant representing an OpenTTD version
|-
| cargotype_available(''cargotype'')
| Check if a certain cargo type is available in this game. ''cargotype'' must be a literal string of length 4.
|-
| railtype_available(''railtype'')
| Check if a railtype is available in this game. ''railtype'' must be a literal string of length 4.
|-
| grf_current_status(''grfid[, mask]'')
| 1 if the given GRF is currently active 0, otherwise. If ''mask'' is set, only the bits set in the mask will be tested. Both parameters must be a literal string of length 4.
|-
| grf_future_status(''grfid[, mask]'')
| Same as above, but tests whether the grf will become active instead of whether it's currently active.
|-
| grf_order_behind(''grfid[, mask]'')
| Same as above, but tests whether current grf will become active in the order behind the referenced grf.
|-
| visual_effect_and_powered(''effect'', ''offset'', ''powered''
| Helper function for the train property visual_effect_and_powered and the VEH_CB_VISUAL_EFFECT_AND_POWERED callback.
|-
| str2number(''4-byte long string'')
| Interpret the given string as a dword and return the value as integer.
|-
| cargotype(''4-byte long string'')
| Return the index of the given cargo type in the cargo translation table.
|-
| railtype(''4-byte long string'')
| Return the index of the given railtype in the railtype translation table.
|-
| reserve_sprites(''number of sprites'')
|
Reserve a number of sprites in the TTD sprite range. This is needed if you want to use your own recolour sprites. Example:
<pre style="color:blue">
param[10] = reserve_sprites(1);
replace(param[10]) {
recolour_sprite {
// your colour remap.
}
}
spritelayout xyz {
building {
...
recolour: param[10];
}
}
</pre>
|-
| int(''v1'')
| Converts v1 to an int. This is done by cutting off everything after the decimal point.
|-
| abs(''v1'')
| Return the absolute value of v1.
|-
| acos / asin / atan / cos / sin / tan
| Standard trigonometric functions.
|-
| CMP(''param1, param2'')
| Compares param1 and param2 (considering them as signed values). Returns CMP_LESS if param1 is less than param2, CMP_EQUAL if they are equal and CMP_GREATER if param1 is greater than param2.
|-
| UCMP(''param1, param2'')
| Compares param1 and param2 (considering them as unsigned values). Returns CMP_LESS if param1 is less than param2, CMP_EQUAL if they are equal and CMP_GREATER if param1 is greater than param2.
|-
| rotate(''value, amount'')
| Rotates ''value'' to the right ''amount'' steps. This is always a 32 bits rotation.
|-
| sound(''soundfile[, volume]'')
| Import sound from .wav-file ''soundfile'' into the grf file and return its numeric ID. Including a file multiple times will not cause it to be duplicated. Loaded sound files must be 8 or 16-bit mono sound files in WAV format, PCM encoding. There are three allowed frequencies: 11025 Hz, 22050 Hz and 44100 Hz. ''volume'' is in the [0, 100] range, the default value (if not set) is 100.
|-
| import_sound(''grfid, id[, volume]'')
| Import sound from a different grf file. ''grfid'' refers to the grf-file to import the sound from. ''id'' is the zero-based internal ID of the sound within the other grf-file. ''volume'' is in the [0, 100] range, the default value (if not set) is 100.
|-
| relative_coord(''x, y'')
| Returns the coordinates in ''0xYYXX'' format. x and y must be in the [0, 255] range.
|-
| num_corners_raised(''slope'')
|
Returns the number of corners raised in a slope. Return value is 0 .. 3 for normal slopes and 4 for steep ones. See also [[NML:List of tile slopes|here]] for more information about slopes. Using this on values that are not slopes results in undefined behaviour.
|-
| slope_to_sprite_offset(''slope'')
|
Returns the sprite offset corresponding to a given slope. Return value is in range 0 .. 18. See also [[NML:List of tile slopes|here]] for more information about slopes. The section on [[NML:Spritelayout|spritelayouts]] contains some more information one possible uses, as well as an example. Using this on values that are not slopes results in undefined behaviour.
|-
| palette_1cc(''colour'')
|
Returns the 1cc palette for the given company colour, see [[List default colour translation palettes#Company colour helper functions|here]] for more info.
|-
| palette_2cc(''colour1'', ''colour2'')
|
Returns the 2cc palette for the given first and second company colour, see [[List default colour translation palettes#Company colour helper functions|here]] for more info.
|-
| vehicle_curv_info(''prev_cur'', ''cur_next'')
| Returns the curvature state of a vehicle, given the direction differences between the (previous-current) and (current-next) vehicle pairs. For use with the vehicle variable <code style="color:darkgreen">curv_info</code>
|-
| format_string(''format'', args)
| Use the python string formatting functions to create a literal string. Keep in mind that the output is a literal string which cannot be used by string(). This function can however be used to create filenames.
|}

NML:Vehicles

2013-05-07T08:42:50Z

Juzza1: /* Variables without parameter */

{{NMLNavPropVarCB}}
== Vehicle IDs ==
Picking an item ID requires keeping two cases in mind: OpenTTD with the engine pool enabled and OpenTTD with engine pool disabled / TTDPatch. The status of the engine pool may be checked with the global variable [[NML:General#General_variables|dynamic_engines]].

=== Engine pool enabled ===
With the engine pool enabled, each NewGRF has its own ID range, NewGRFs don't influence each other. IDs may freely be chosen between 0 and 65535. If the chosen ID belongs to an existing vehicle, this vehicle is overridden by your vehicle. If another NewGRF is already overriding that vehicle, a new vehicle will be allocated, but all the properties will be copied from the old vehicle. If you define an ID for which no original vehicle exists, a new (blank) vehicle is allocated.

This behaviour can be modified using an [[NML:Overriding_vehicles_in_other_NewGRFs|engine_override]], this allows changing the properties of vehicles defined in other NewGRFs instead of allocating a new vehicle.

=== TTDPatch / Engine pool disabled ===
Each new vehicle has to replace an existing vehicle. If multiple NewGRFs try to replace the same vehicle, the last NewGRF loaded 'wins'. [[VehicleIDs|This page]] contains a list of valid vehicle IDs for each vehicle type, look in the 'NML ID' column. Note that IDs are not bound to a specific sort of vehicle (e.g. monorail wagons) but to a feature (e.g. trains, road vehicles).

In general, you should take the following steps:
* If your NewGRF is intended as a complete replacement for the default vehicles, disable the relevant default vehicles using [[NML:Disable_items|disable_item]].
* Re-use IDs of existing vehicles as much as possible.
* If your NewGRF uses IDs outside of the normal range (for example, because you there are more vehicles than slots available), let your code check if dynamic_engies is enabled. If not, skip the vehicles outside the normal range (using an if-statement) and make sure that the remaining vehicles allow for reasonable gameplay. It is recommended to issue a warning to the user about this. Alternatively, it is also possible to disable your entire NewGRF. If you don't do this check and dynamic_engines is off, OpenTTD may disable your NewGRF with the somewhat cryptic message 'Attempt to use invalid ID', which will likely lead to bug reports about your NewGRF and/or your OpenTTD.

==Properties common to all vehicle types==

{| class="t"
! property
! value range
! available for articulated vehicle
! comment
|-
| <code style="color:green">name</code>
| (string)
| yes
| for example <code style="color:darkgreen">string(STR_NAME_HEREFORD_TRAM)</code>
|-
| <code style="color:green">climates_available</code>
| bitmask(CLIMATE_XXX, CLIMATE_YYY, ...)
| set to <code style="color:green">NO_CLIMATE</code>
|
;CLIMATE_TEMPERATE
;CLIMATE_ARCTIC
;CLIMATE_TROPICAL
;CLIMATE_TOYLAND
;NO_CLIMATE
:Vehicle is availble in no climate (e.g. for articulated parts)
;ALL_CLIMATES
:Vehicle is available irrespective of climate

To make a vehicle available in all climates except toyland you could use: <code style="color:green">ALL_CLIMATES & ~bitmask(CLIMATE_TOYLAND)</code>.
|-
| <code style="color:green">introduction_date</code>
| <code style="color:green">date</code>(yyyy,mm,dd)
| no
| Valid range for yyyy is 0 ... 5000000. In TTDPatch, dates after 2044 will be limited to 2044. Unless the engine is introduced within two years after game-start (always 1920 in TTDPatch), a random number of days between 0 and 511 will be added to this.
|-
| <code style="color:green">model_life</code>
| 0 ... 254 (years) or <code style="color:green">VEHICLE_NEVER_EXPIRES</code>
| no
|
Number of years a model is "supported" by the manufacturer, see [[#Engine life cycle|below]].
|-
| <code style="color:green">retire_early</code>
| -128 ... 127 (years)
| no
|
Retire the vehicle (make it unavailable in the purchase menu) this many years before reliability starts dropping, see [[#Engine life cycle|below]]. May be negative.
|-
| <code style="color:green">vehicle_life</code>
| 0 ... 255 (years)
| no
| Life length of an individual vehicle, before it is considered too old and in need of replacement.
|-
| <code style="color:green">reliability_decay</code>
| 0 ... 255
| no
| Default vehicles use 20. The higher the value the faster reliability decays, the more frequent service is needed. 0 means reliability never decreases if the vehicle is not too old
|-
| <code style="color:green">refittable_cargo_classes</code>
|
bit set of [[NML:Cargos#Cargo classes|cargo classes]]
| yes
| for example: <code style="color:darkgreen">bitmask(CC_BULK, CC_COVERED)</code>
|-
| <code style="color:green">non_refittable_cargo_classes</code>
|
bit set of [[NML:Cargos#Cargo classes|cargo classes]]
| yes
| for example: <code style="color:darkgreen">bitmask(CC_OVERSIZED, CC_SPECIAL)</code>
|-
| <code style="color:green">refittable_cargo_types</code>
| bit mask of entries into the cargo translation table
| yes
| As of NML 0.3, do not use this. Use cargo_[dis]allow_refit (see below) instead.
|-
| <code style="color:green">cargo_allow_refit</code>
| Array of cargo labels from the [[NML:Cargotable|cargotable]]
| Yes
| {{ottdp|1.2|no|ottdrev=r23291}} A list of cargo types to allow refitting to, irrespective of cargo classes. Example: <code style="color:darkgreen">[COAL, IORE]</code>
|-
| <code style="color:green">cargo_disallow_refit</code>
| Array of cargo labels from the [[NML:Cargotable|cargotable]]
| Yes
| {{ottdp|1.2|no|ottdrev=r23291}} A list of cargo types to disallow refitting to, irrespective of cargo classes. Example: <code style="color:darkgreen">[MAIL]</code>
|-
| <code style="color:green">loading_speed</code>
| 0 ... 255 (cargo units)
| yes
| Units of cargo loaded per time unit. Default vehicles use 5 for trains and road vehicles, 10 for ships and 20 for aircraft. This amount of cargo is loaded to or unloaded from the vehicle every 40 ticks for trains, every 20 ticks for road vehicles and aircraft and every 10 ticks for ships.
|-
| <code style="color:green">cost_factor</code>
| 0 ... 255
| Set to 0
| multiplier to the base purchase cost
|-
| <code style="color:green">running_cost_factor</code>
| 0 ... 255
| Set to 0
| multiplier to the base running costs
|-
| <code style="color:green">cargo_age_period</code>
| 0 ... 65535
| yes
|
{{ottd|1.2|r22713}} This property specifies after how many ticks cargo is aged. Default value is 185. 74 ticks is equal to 1 day.
|}

===Refittability===

To determine whether your vehicle can be refitted to a certain cargo, OpenTTD uses the following table

{| class="t"
! Cargo matches refittable_cargo_classes
! Cargo matches non_refittable_cargo_classes
! Cargo in cargo_allow_refit
! Cargo in cargo_disallow_refit
! Result
|-
| Yes
| No
| Doesn't matter
| No
| Refittable
|-
| No
| Doesn't matter
| No
| Doesn't matter
| Not refittable
|-
| Doesn't matter
| Doesn't matter
| Yes
| No
| Refittable
|-
| Doesn't matter
| Doesn't matter
| Doesn't matter
| Yes
| Not refittable
|}

For those that prefer boolean logic, the formula is as follows:

refittable = ((cargo classes in refittable_cargo_classes AND NOT cargo classes in non_refittable_cargo_classes) OR cargo in cargo_allow_refit) AND NOT (cargo in cargo_disallow_refit)

In general, you should use refittable_cargo_classes and non_refittable_cargo_classes to decide to which cargos your vehicle is refittable, and only then use cargo_allow_refit and cargo_disallow_refit to allow/disallow specific cargos.

===Engine life cycle===

The life cycle of a vehicle model consists of three phases, as outlined in the following table.

{| class="t"
! phase
! duration
! reliability
|-
| 1
| 7 to 38 months
| increases from 48-73% to 75-100%
|-
| 2
| <code style="color:darkgreen">model_life</code> - 8 years
| stays constant at peak, 75-100%
|-
| 3
| 10 to 20.5 years
| decreases from peak to 25-50%
|}

If <code style="color:darkgreen">model_life</code> is set to <code style="color:darkgreen">VEHICLE_NEVER_EXPIRES</code>, the engine remains in phase 2 forever.

Normally, the vehicle is removed from the purchase menu at the and of phase 3. However if you set the <code style="color:darkgreen">retire_early</code> property, it will be retired this many years before (or after, if the value is negative) the end of phase 2.

==Sorting vehicles in the purchase list==
This is a special property that is not encoded in an item/property-block like most other properties but it has it's own block instead. The syntax is as follows:

sort(<feature>, [<ID>, <ID>, <ID>...]);

The engines will be sorted in the given order on the position where originally the first element was. Say the original engine sorting is this: A B C D E and you use this code <code style="color:darkgreen">sort(FEAT_TRAINS, [D, B, A]);</code> the final sorting will be this: C D B A E

==Train properties==

{| class="t"
! property
! value range
! available for articulated vehicle
! comment
|-
| <code style="color:green">sprite_id</code>
| <code style="color:green">SPRITE_ID_NEW_TRAIN</code>
| yes
| Set this property to enable new graphics
|-
| <code style="color:green">speed</code>
| 0 ... 65000 (float, speed units)
| no
| Max speed for engines, speed limit for wagons
|-
| <code style="color:green">misc_flags</code>
| bitmask(TRAIN_FLAG_XXX, ...)
| FLIP should not be set, TILT and MU TO the same value as the 1st part
|
;TRAIN_FLAG_TILT
: enable the tilt bonus (20% speed in curves, if all vehicles in consist have it set)
;TRAIN_FLAG_2CC
:Enable use of the 2nd company colour
;TRAIN_FLAG_MU
:act as multiple unit (used for livery selection only)
;TRAIN_FLAG_FLIP
:Allow vehicle to be flipped (reversed) in depot
;TRAIN_FLAG_AUTOREFIT
:Allow autoreffitting. To enable autorefit, furthermore the [[#Vehicle callbacks|refit_cost]]-callback has to allow it, or else (if this callback is not implemented or fails) the <code style="color:green">refit_cost</code>-property (see below) must be set to 0.
;TRAIN_FLAG_NO_BREAKDOWN_SMOKE
:{{nml|0.3}} {{ottdp|1.3|no|ottdrev=r24124}} Disable breakdown smoke effect
|-
| <code style="color:green">refit_cost</code>
| 0 ... 255
| yes
| in 50% units of the purchase price cost base
|-
| <code style="color:green">callback_flags</code>
| bitmask(VEH_CBF_XXX, ...)
| yes
|
Do not set this, unless you use [[NML:Old style callbacks|old-style callbacks]].
|-
| <code style="color:green">track_type</code>
| item from railtypetable
| must be the same as front
| Default railtype table: RAIL, MONO, MGLV. If you install a railtypetable yourself you'll always get the railtype you specified. If you want a vehicle to run on electric rail and you don't have a railtypetable, set <code style="color:green">track_type</code> to RAIL and make sure that you set <code style="color:green">engine_class</code> to <code style="color:green">ENGINE_CLASS_ELECTRIC</code>.
|-
| <code style="color:green">ai_special_flag</code>
| [<code style="color:green">AI_FLAG_PASSENGER</code> <nowiki>|</nowiki> <code style="color:green">AI_FLAG_CARGO</code>]
| no
|
;<code style="color:green">AI_FLAG_PASSENGER</code>
:Tell computer players that it's an engine that should only be used for passenger service.
|-
| <code style="color:green">power</code>
| 0 ... 65000 hp (float, power units)
| Set to 0
|
|-
| <code style="color:green">running_cost_base</code>
| RUNNING_COST_XXX
| Set to RUNNING_COST_NONE
|
;RUNNING_COST_STEAM
;RUNNING_COST_DIESEL
;RUNNING_COST_ELECTRIC
;RUNNING_COST_ROADVEH
;RUNNING_COST_NONE
:no running costs
|-
| <code style="color:green">dual_headed</code>
| [0 <nowiki>|</nowiki> 1]
| Set to 0 for all parts of an articulated vehicle
| 1 = dual_headed, otherwise normal engine
|-
| <code style="color:green">default_cargo_type</code>
| An identifier from the [[NML:Cargotable|cargo table]], or DEFAULT_CARGO_FIRST_REFITTABLE
| Yes
| If the vehicle is refittable to at least one cargo, but the chosen default cargo is not available or is set to DEFAULT_CARGO_FIRST_REFITTABLE, then the first refittable cargo is used. The first refittable is chosen according to the order in your [[NML:Cargotable|cargo table]]. If this property is set to a valid cargo but the vehicle cannot refit to any cargo type, then the vehicle will be able to carry only this cargo, but it cannot be refitted (like e.g. the default train wagons).
|-
| <code style="color:green">cargo_capacity</code>
| 0 .. 255
| yes
| By default, passenger capacity is 4x, and mail/goods capacity 2x larger than capacity for other cargoes. The capacity set here is used for the default (i.e. first refittable) cargo. Use the <code style="color:green">cargo_capacity</code> callback to avoid this effect.
|-
| <code style="color:green">weight</code>
| 0 .. 1279 ton (float, mass units)
| Set to 0
|
|-
| <code style="color:green">ai_engine_rank</code>
| 0 ... 255
| no
| TTDPatch only: Higher values make the engine for the TTDPatch AI more attractive
|-
| <code style="color:green">engine_class</code>
| ENGINE_CLASS_XXX
| no
|
Defines which livery colour settings apply to the vehicle
;ENGINE_CLASS_STEAM
;ENGINE_CLASS_DIESEL
;ENGINE_CLASS_ELECTRIC
;ENGINE_CLASS_MONORAIL
;ENGINE_CLASS_MAGLEV
|-
| <code style="color:green">extra_power_per_wagon</code>
| 0 ... 65000 hp (float, power units)
| Set to 0
| Only wagons with a livery override for this engine will add power
|-
| <code style="color:green">tractive_effort_coefficient</code>
| 0 ... 1 (float)
| Set to 0
| Fraction of the vehicle weight that is available as tractive effort. Tractive effort (in kN) is calculated as (TE coefficient) * 10 * weight (in tons), with 10 being an approximation of the acceleration of gravity (9.81 m/s). Default value is 0.3.
|-
| <code style="color:green">air_drag_coefficient</code>
| 0 ... 1 (float)
| Set to 0
| Coefficient of the relative air drag, in arbitrary units. The default value is approximately (8 / max_speed), with max_speed in km/h, clamped to the range 0.004 .. 0.75.
|-
| <code style="color:green">length</code>
| 1 ... 8
| yes
| Length of the vehicle in arbitrary units. Use a value of 8 (equal to the predefined constant VEHICLE_LENGTH) for a full-length vehicle.
|-
| <code style="color:green">visual_effect_and_powered</code>
| <code style="color:green">visual_effect_and_powered</code> (VISUAL_EFFECT_XXX, offset, <code style="color:green">ENABLE_WAGON_POWER</code> or <code style="color:green">DISABLE_WAGON_POWER</code>)
| yes
|
Set the type of visual effect for the vehicle and its positional offset with respect to the vehicle. An offset of 0 is default, negative values mean more to the front and positive values are backwards. Minimum offset is -8, maximum is 7.

;VISUAL_EFFECT_DEFAULT
:No effect, unless for the default vehicles
;VISUAL_EFFECT_STEAM
:Steam like from steam engine
;VISUAL_EFFECT_DIESEL
:Steam from internal combustion engine
;VISUAL_EFFECT_ELECTRIC
:Electric sparks
;VISUAL_EFFECT_DISABLE
:No effect
|-
| <code style="color:green">extra_weight_per_wagon</code>
| 0 ... 255 ton (float, mass units)
| Set to 0
| Adds extra weight for powered wagons, see <code style="color:green">extra_power_per_wagon</code>
|-
| <code style="color:green">bitmask_vehicle_info</code>
| 8-bit bitmask
| yes
|
Used for obtaining [[#bitmask consist info|<code style="color:green">bitmask_consist_info</code>]]
|}

==Road vehicle properties==

{| class="t"
! property
! value range
! available for articulated vehicle
! comment
|-
| sprite_id
| SPRITE_ID_NEW_ROADVEH
| yes
| Set this property to enable new graphics
|-
| speed
| 0 ... 514km/h (float, speed units)
| no
|
|-
| misc_flags
| bitmask(ROADVEH_FLAG_XXX, ...)
| partly; tram flag must the same
|
;ROADVEH_FLAG_TRAM
:The vehicle requires tram tracks to run on
;ROADVEH_FLAG_2CC
:Enable 2nd company colour
;ROADVEH_FLAG_AUTOREFIT
:Allow autorefitting. To enable autorefit, furthermore the [[#Vehicle callbacks|refit_cost]]-callback has to allow it, or else (if this callback is not implemented or fails) the <code style="color:green">refit_cost</code>-property (see below) must be set to 0.
;ROADVEH_FLAG_NO_BREAKDOWN_SMOKE
:{{nml|0.3}} {{ottdp|1.3|no|ottdrev=r24124}} Disable breakdown smoke effect
|-
| refit_cost
| 0 ... 255
| yes
| in 25% units of the purchase price cost base
|-
| callback_flags
| bitmask(VEH_CBF_XXX, ...)
| yes
|
Do not set this, unless you use [[NML:Old style callbacks|old-style callbacks]].
|-
| running_cost_base
| RUNNING_COST_XXX
| set to RUNNING_COST_NONE
|
;RUNNING_COST_STEAM
;RUNNING_COST_DIESEL
;RUNNING_COST_ELECTRIC
;RUNNING_COST_ROADVEH
;RUNNING_COST_NONE
:no running costs
|-
| power
| 0 ... 2550hp (float, power units)
| Set to 0
|
|-
| weight
| 0 ... 63.75ton (float, mass units)
| Set to 0
|
|-
| tractive_effort_coefficient
| 0 ... 1 (float)
| Set to 0
| Fraction of the vehicle weight that is available as tractive effort. Tractive effort (in kN) is calculated as (TE coefficient) * 10 * weight (in tons), with 10 being an approximation of the acceleration of gravity (9.81 m/s). Default value is 0.3.
|-
| air_drag_coefficient
| 0 ... 1 (float)
| Set to 0
| Coefficient of the relative air drag, in arbitrary units. The default value is approximately (8 / max_speed), with max_speed in km/h, clamped to the range 0.004 .. 0.75.
|-
| <code style="color:green">default_cargo_type</code>
| An identifier from the [[NML:Cargotable|cargo table]], or DEFAULT_CARGO_FIRST_REFITTABLE
| Yes
| If the vehicle is refittable to at least one cargo, but the chosen default cargo is not available or is set to DEFAULT_CARGO_FIRST_REFITTABLE, then the first refittable cargo is used. The first refittable is chosen according to the order in your [[NML:Cargotable|cargo table]]. If this property is set to a valid cargo but the vehicle cannot refit to any cargo type, then the vehicle will be able to carry only this cargo, but it cannot be refitted (like e.g. the default train wagons).
|-
| cargo_capacity
| 0 ... 255
| yes
| By default, passenger capacity is 4x, and mail/goods capacity 2x larger than capacity for other cargoes. The capacity set here is used for the default (i.e. first refittable) cargo. Use the <code style="color:green">cargo_capacity</code> callback to avoid this effect.
|-
| sound_effect
| SOUND_XXX
| no
|
See available [[NML:List of sound effects|sound effects]].
|-
| visual_effect
| visual_effect( VISUAL_EFFECT_XXX, offset)
| yes
|
Set the type of visual effect for the vehicle and its positional offset with respect to the vehicle. An offset of 0 is default, negative values mean more to the front and positive values are backwards. Minimum offset is -8, maximum is 7.

;VISUAL_EFFECT_DEFAULT
:No effect, unless for the default vehicles
;VISUAL_EFFECT_STEAM
:Steam like from steam engine
;VISUAL_EFFECT_DIESEL
:Steam from internal combustion engine
;VISUAL_EFFECT_ELECTRIC
:Electric sparks
;VISUAL_EFFECT_DISABLE
:No effect
|-
| length
| 1 ... 8
| yes
| Length of the vehicle in arbitrary units. Use a value of 8 (equal to the predefined constant VEHICLE_LENGTH) for a full-length vehicle.
|}

==Ship properties==

{| class="t"
! property
! value range
! comment
|-
| sprite_id
| SPRITE_ID_NEW_SHIP
| Set this property to enable new graphics
|-
| speed
| 0 ... 127 km/h (float, speed units)
|
|-
| misc_flags
| bitmask(SHIP_FLAG_XXX)
| Bitmask with to possible flags, set to 0 to disable all.

;SHIP_FLAG_2CC
:Enable use of the 2nd company colour
;SHIP_FLAG_AUTOREFIT
:llow autorefitting. To enable autorefit, furthermore the [[#Vehicle callbacks|refit_cost]]-callback has to allow it, or else (if this callback is not implemented or fails) the <code style="color:green">refit_cost</code>-property (see below) must be set to 0.
;SHIP_FLAG_NO_BREAKDOWN_SMOKE
:{{nml|0.3}} {{ottdp|1.3|no|ottdrev=r24124}} Disable breakdown smoke effect
|-
| refit_cost
| 0 ... 255
| in 1/32 of the default refit cost base
|-
| callback_flags
| bitmask(VEH_CBF_XXX, ...)
|
Do not set this, unless you use [[NML:Old style callbacks|old-style callbacks]].
|-
| is_refittable
| [0 <nowiki>|</nowiki> 1]
| 0=false, 1=true. Note: if you do not set this property to 1, then refittable_cargo_classes / non_refittable_cargo_classes have no effect.
|-
| <code style="color:green">default_cargo_type</code>
| An identifier from the [[NML:Cargotable|cargo table]], or DEFAULT_CARGO_FIRST_REFITTABLE
| If the vehicle is refittable to at least one cargo, but the chosen default cargo is not available or is set to DEFAULT_CARGO_FIRST_REFITTABLE, then the first refittable cargo is used. The first refittable is chosen according to the order in your [[NML:Cargotable|cargo table]]. If this property is set to a valid cargo but the vehicle cannot refit to any cargo type, then the vehicle will be able to carry only this cargo, but it cannot be refitted (like e.g. the default train wagons).
|-
| cargo_capacity
| 0 ... 255
| For ships (unlike other vehicle types) the capacity set here is not affected by the cargo type.
|-
| sound_effect
| SOUND_XXX
|
See available [[NML:List of sound effects|sound effects]].
|-
| ocean_speed_fraction
| 0 ... 1 (float)
|
{{ottd|1.2|r22639}} fraction of base speed on ocean tiles (default: 1)
|-
| canal_speed_fraction
| 0 ... 1 (float)
|
{{ottd|1.2|r22639}} fraction of base speed on canal tiles (default: 1)
|-
| visual_effect
| visual_effect(VISUAL_EFFECT_XXX, offset)
| XXX=[DEFAULT <nowiki>|</nowiki> STEAM <nowiki>|</nowiki> DIESEL <nowiki>|</nowiki> ELECTRIC <nowiki>|</nowiki> DISABLE], it is the type of the visual effect you want for this ship. Default means no effect. Offset is the position of the effect. 0 is default, negative values mean more to the front and positive values are backwards. Minimum offset is -8, maximum is 7.
|}

==Aircraft properties==

{| class="t"
! property
! value range
! comment
|-
| sprite_id
| SPRITE_ID_NEW_AIRCRAFT
| Set this property to enable new graphics
|-
| speed
| 0 .. 3280 km/h (float, speed units)
|
|-
| range
| 0 .. 2894
| {{nml|0.3}} {{ottdp|1.2|no|ottdrev=r23504}} Maximum (euclidean) distance the aircraft can cover between two airports. Set to 0 for unlimited range.
|-
| misc_flags
| bitmask(AIRCRAFT_FLAG_2CC, AIRCRAFT_FLAG_AUTOREFIT)
| Bitmask with to possible flags, set to 0 to disable all.

;AIRCRAFT_FLAG_2CC
:Enable 2nd company colour
;AIRCRAFT_FLAG_AUTOREFIT
:Allow autorefitting. To enable autorefit, furthermore the [[#Vehicle callbacks|refit_cost]]-callback has to allow it, or else (if this callback is not implemented or fails) the <code style="color:green">refit_cost</code>-property (see below) must be set to 0.
;AIRCRAFT_FLAG_NO_BREAKDOWN_SMOKE
:{{nml|0.3}} {{ottdp|1.3|no|ottdrev=r24124}} Disable breakdown smoke effect
|-
| refit_cost
| 0 ... 255
| in 1/32 of default refit cost base
|-
| callback_flags
| bitmask(VEH_CBF_XXX, ...)
|
Do not set this, unless you use [[NML:Old style callbacks|old-style callbacks]].
|-
| aircraft_type
| AIRCRAFT_TYPE_XXX
|
;AIRCRAFT_TYPE_HELICOPTER
:Can land on helipad
;AIRCRAFT_TYPE_SMALL
:Can land on all airports with runway
;AIRCRAFT_TYPE_LARGE
:Can land on all airports with runway. But have a high crash chance on small airports
|-
| acceleration
| {{ottd|1.3.1}} 0 ... 255 {{ottd|<1.3.1}} 0 ... 19
| {{ottd|1.3.1}} Default aircraft use values in the range 18 to 50 (= 6.75 to 18.75 mph/tick = 499.5 to 1387.5 mph/day), which is generally considered quite fast. 
{{ottd|<1.3.1}} In older OpenTTD, aircraft provided by NewGRF accelerate 166% faster than intended.
|-
| passenger_capacity
| 0 ... 65536
| Capacity for the passenger compartment. See also the notes at <code style="color:darkgreen">mail_capacity</code> below.
|-
| mail_capacity
| 0 ... 255
| Capacity for the mail compartment, if refitted to a cargo in the CC_PASSENGERS class. When refitted to other cargoes, this capacity is added to the passenger capacity to determine the base capacity. The actual capacity is set to this base capacity divided by 1 for mail, 2 for goods and 4 for all other cargoes. To override this effect, use the <code style="color:darkgreen">passenger_capacity</code> and <code style="color:darkgreen">mail_capacity</code> callbacks.
|-
| sound_effect
| SOUND_XXX
|
See available [[NML:List of sound effects|sound effects]].
|}

==Vehicle variables==

Below an overview of all vehicle-specific variables. Not that in the purchase list, the vehicle is not built yet and as such many variables are not available. All general variables are available, refer to the table for info on vehicle-specific variables. Trying to access a non-available variable invokes undefined behaviour. Please note that while all variables are available for all vehicles types, some of them only make sense for one or more vehicle types. For example checking current_railtype for a non-rail vehicle doesn't make sense at all.

===Variables without parameter===

{| class="t"
! name
! value range
! available in purchase list?
! comment
|-
| position_in_consist
| 0 ... 255
| No
| The position of the current vehicle-part from the start of the vehicle. The engine will get value 0, the first wagon (or second engine) gets value 1, etc.
|-
| position_in_consist_from_end
| 0 ... 255
| No
| Same as position_in_consist but counted from the end. The last wagon will get value 0.
|-
| num_vehs_in_consist
| 1 ... 256
| No
| The total number of vehicles-parts in this vehicle. For aircraft this will include the shadow and the rotor.
|-
| position_in_vehid_chain
| 0 ... 255
| No
| See position_in_consist, but not of the complete vehicle but only all consecutive parts with the same id.
|-
| position_in_vehid_chain_from_end
| 0 ... 255
| No
| See position_in_consist_from_end, but not of the complete vehicle but only all consecutive parts with the same id.
|-
| num_vehs_in_vehid_chain
| 1 ... 256
| No
| See num_vehs_in_consist, but not of the complete vehicle but only all consecutive parts with the same id.
|-
| cargo_classes_in_consist
| Bitmask of CC_XXX
| No
|
[[NML:Cargos#Cargo classes|cargo classes]]
|-
| most_common_refit
|
[[NML:Cargos#Cargo properties|cargo class]]
| No
| cargo class most often refit to
|-
| bitmask_consist_info
| Bitmask 8 bit
| No
|
Binary OR of the values of [[#bitmask vehicle info|bitmask_vehicle_info]] of all vehicles (engines, wagons) in the consist. Only available for rail vehicles.
|-
| company_num
| 0 ... 14
| Yes
| company number of the vehicle owner. TTDPatch only supports up to 8 companies (0 ... 7)
|-
| company_type
| PLAYERTYPE_XX
| Yes
|
;PLAYERTYPE_HUMAN
:human player
;PLAYERTYPE_AI
:AI player
;PLAYERTYPE_HUMAN_IN_AI
:human managing AI company
;PLAYERTYPE_AI_IN_HUMAN
:AI managing human company

OpenTTD only uses PLAYERTYPE_HUMAN and PLAYERTYPE_AI. If you cheat yourself to be part of an AI company OpenTTD will still report PLAYERTYPE_AI for the company with yourself and the AI and it'll report PLAYERTYPE_HUMAN for the now uncontrolled company.
|-
| company_colour1
| COLOUR_XXX
| Yes
|
Refer to the table [[NML:List of default colour translation palettes#Company colour helper functions|here]] for possible values.
|-
| company_colour2
| COLOUR_XXX
| Yes
|
Same as company_colour1, if no 2nd company colour is chosen. Refer to the table [[NML:List of default colour translation palettes#Company colour helper functions|here]] for possible values.
|-
| aircraft_height
| 0 ... 255
| No
| Height difference between the aircraft and its shadow. 8 Units are equivalent to one height level on the map.
|-
| airport_type
| AIRPORTTYPE_XX
| No
|
;AIRPORTTYPE_SMALL
;AIRPORTTYPE_LARGE
;AIRPORTTYPE_HELIPORT
;AIRPORTTYPE_OILRIG
|-
| curv_info_prev_cur
| -2 ... 2
| No
| Difference in direction between the previous (towards engine) vehicle and this vehicle. Curvature to the right is positive. 1 unit is 45 degrees.
|-
| curv_info_cur_next
| -2 ... 2
| No
| Difference in direction between this vehicle and the next (towards rear end) vehicle. Curvature to the right is positive. 1 unit is 45 degrees.
|-
| curv_info_prev_next
| -4 ... 4
| No
| Difference in direction between the previous (towards engine) and next (towards rear end) vehicle. Curvature to the right is positive. 1 unit is 45 degrees. Equal to <code style="color:darkgreen">curve_invo_prev_cur + curv_info_cur_next</code>.
|-
| curv_info
| vehicle_curv_info(''prev_cur'', ''cur_next'')''''
| No
|
Returns a magic number that represents the curvature state of the prev-cur-next vehicle triplet. Do not try to make sense of this magic number, use the [[NML:Builtin functions|builtin function]] <code style="color:darkgreen">vehicle_curv_info()</code> instead to make comparisons. <code style="color:darkgreen">curv_info == vehicle_curv_info(a, b)</code> is equivalent to <code style="color:darkgreen">(curv_info_prev_cur == a) && (curv_info_cur_next == b)</code>, however the former can easily be used in a switch-block.
|-
| motion_counter
| 0 ... 15
| Yes, always 0
| Is increased every time the vehicle moves a single step on the map. Useful for animations.
|-
| cargo_type_in_veh
| entry in cargo translation table
| Yes, for the default cargo
| 0xFF if not present in the table
|-
| cargo_unit_weight
| weight per unit in 1/16t
| Yes, for the default cargo
|
|-
| cargo_classes
| Bitmask of [[NML:Cargos#Cargo properties|cargo class]]
| Yes, for the default cargo
| class of the currently transported cargo
|-
| vehicle_is_available
| [0 <nowiki>|</nowiki> 1]
| Yes
| Value is 1 if the vehicle is available on the open market
|-
| vehicle_is_testing
| [0 <nowiki>|</nowiki> 1]
| Yes
| Value is 1 if the vehicle is currently being tested
|-
| vehicle_is_offered
| [0 <nowiki>|</nowiki> 1]
| Yes
| Value is 1 if the vehicle is currently being offered for exclusive preview
|-
| build_year
| 0 ... 5000000
| Yes
| 0-based year when the vehicle was built, current year if the vehicle is not built yet
|-
| direction
| DIRECTION_XX
| No
|
See [[NML:List of direction constants|here]] for an overview of possible values and their meaning.
|-
| cargo_capacity
| 0 ... 65535
| No
| Cargo capacity (number of units) of the vehicle
|-
| cargo_count
| 0 ... 65535
| No
| Number of cargo units of cargo in the vehicle
|-
| cargo_subtype
| 0 ... 255
| Yes, always 0
| Cargo subtype, used to provide more than one refit option for the same cargo type. See also the <code style="color:darkgreen">cargo_subtype_text</code> callback.
|-
| vehicle_is_powered
| [0 <nowiki>|</nowiki> 1]
| No
| Vehicle provides power and is on the correct track type
|-
| vehicle_is_not_powered
| [0 <nowiki>|</nowiki> 1]
| No
| Vehicle is either on a wrong track type or it doesn't provide power at all
|-
| vehicle_is_potentially_powered
| [0 <nowiki>|</nowiki> 1]
| No
| Vehicle provides power, if it is on a suitable track type
|-
| vehicle_is_reversed
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle has reversed an odd number of times
|-
| built_during_preview
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle was built during the exclusive preview stage
|-
| current_railtype
| No
| Entry from railtype translation table or 0xFF
| Don't use this variable unless you've defined a railtype translation table. If the train is running on a railtype that is not listed in your railtype translation table this variable will contain 0xFF. Available since OpenTTD r20164.
|-
| waiting_triggers
|
| No
|
Random triggers waiting to be matched. (see [[NML:Random switch|Random switch]])
|-
| random_bits
| 0 ... 255
| No
|
Random data that can be used to randomize certain descisions. (see [[NML:Random switch|Random switch]])
|-
| grfid
| 0 ... 0xFFFFFFFF
| No
|
GRFID that defined the [[NML:Graphics|graphics]]-block for this vehicle. To compare this with other grfids, use the [[NML:Builtin functions|builtin function]] <code style="color:darkgreen">str2number()</code> to convert the other GRFID to a number as well.
|-
| vehicle_type_id
| 0 ... 65535 or a name defined in item block
| No
| GRF-local ID of the vehicle, equal to the item ID. Note that vehicles from other NewGRFs may have the same ID, so you'll generally have to check the <code style="color:darkgreen">grfid</code> as well.
|-
| vehicle_is_hidden
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle is hidden in a depot or tunnel.
|-
| vehicle_is_stopped
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle is stopped, or if it is braking for a stop (trains only).
|-
| vehicle_is_crashed
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle has crashed.
|-
| vehicle_is_broken
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle is broken down.
|-
| date_of_last_service
| date(year, month, day)
| No
|
|-
| breakdowns_since_last_service
| 0 ... 255
| No
| Number of breakdowns since the last service
|-
| reliability
| 0 ... 100
| No
| Reliability (percentage)
|-
| age_in_days
| 0 ... 65535
| No
| Vehicle age in days.
|-
| max_age_in_days
| 0 ... 65535
| No
| Maximum vehicle age in days.
|-
| current_speed
| (speed units)
| No
| The current speed of the vehicle in m/s
|-
| max_speed
| (speed units)
| No
| The maximum speed of the vehicle in m/s
|-
| current_max_speed
| (speed units)
| No
| {{nml|0.3}} {{ottdp|1.3|no|ottdrev=r24246}} Current maximum speed of the vehicle in m/s. This includes e.g. track or timetable limits. Only valid for front vehicle.
|-
| vehicle_is_in_depot
| [0 <nowiki>|</nowiki> 1]
| No
| Value is 1 if the vehicle is inside a depot
|}

===Variables that require an argument===

{| class="t"
! name
! Argument
! value range
! available in purchase list?
! comment
|-
| count_veh_id
| The vehicle ID to look for.
| 0..255
| No
| The number of vehicles in the current consist that have the given ID.
|-
| other_veh_curv_info
| Offset in the chain from the current vehicle.<ref name="offset">Value range is -128..127. Positive values are interpreted as towards the end, negative values as towards the front. If the offset is outside the vehicle chain, the result value will be 0.</ref>
| -4..4
| No
| Difference in direction between the other vehicle and this vehicle. Curvature to the right is positive. 1 unit is 45 degrees.
|-
| other_veh_is_hidden
| Offset in the chain from the current vehicle.<ref name="offset"/>
| [0 <nowiki>|</nowiki> 1]
| No
| 1 the other vehicle is hidden in a depot or tunnel, 0 otherwise
|-
| other_veh_x_offset
| Offset in the chain from the current vehicle.<ref name="offset"/>
| -128..127
| No
| Signed difference in X-position (top-right to bottom-left) between the other vehicle and this vehicle.
|-
| other_veh_x_offset
| Offset in the chain from the current vehicle.<ref name="offset"/>
| -128..127
| No
| Signed difference in Y-position (top-left to bottom-right) between the other vehicle and this vehicle.
|-
| other_veh_is_hidden
| Offset in the chain from the current vehicle.<ref name="offset"/>
| -128..127
| No
| Signed difference in Z-position (upwards) between the other vehicle and this vehicle.
|}
<references/>

==Vehicle callbacks==
The following table contains a list of available vehicle callbacks. Additionally, it's possible to provide cargo-specific graphics, using the identifier from the [[NML:Cargotable|cargo table]] as callback name. These callbacks will be used if the vehicle is refitted to the corresponding cargo type. If no cargo-specific graphics match the cargo that the vehicle is carrying, the <code style="color:darkgreen">default</code> callback is used instead. Cargo-specific graphics callbacks are never called from the purchase menu, refer to the <code style="color:darkgreen">purchase</code> callback below instead.

Note that the above affects '''graphics only''', other callbacks are unaffected.

{| class="t"
! Name
! Available for
! In purchase menu?
! value range
! comment
|-
| default
| All
| Yes, unless <code style="color:darkgreen">purchase</code> is set separately
| Sprite group
| 'Normal' vehicle graphics, if no cargo-specific graphics apply. See also the section on [[#Sprites in GUI|GUI sprites]].
|-
| purchase
| All
| Yes, only
| Sprite group
| Graphics to show in the buy menu (only the horizontal view is needed, except for dual-headed trains. With the <code>dual_headed</code> property set, special rules for the purchase menu sprite apply: two sprites are drawn (for front and back) as if the vehicle is normally constructed. If you supply one purchase menu sprite, it will be used for both vehicle parts in the purchase menu. Provide a set of 8 sprites, and the 7th resp. 3rd sprite will be drawn; provide a set of 8 blank sprites except the 7th if you want to fully control a single purchase menu sprite for a dual-headed engine. ) See also the section on [[#Sprites in GUI|GUI sprites]].
|-
| rotor
| Aircraft (helicopters)
| No
| Sprite group
| Graphics for the helicopter rotor (4 sprites; 1 stopped and 3 moving)
|-
| random_trigger
| All
| No
| N/A
| See [[NML:Random switch|random switch]] for more information.
|-
| cargo_subtype_text
| All
| No
| String, or CB_RESULT_NO_TEXT
| With this callback, you can display extra text after the cargo in the vehicle information window. This callback is called during refitting, with succesively increased values of the <code style="color:darkgreen">cargo_subtype</code> variable, until the callback returns CB_RESULT_NO_TEXT. All returned strings are then displayed as refit options. The chosen refit option is saved in the <code style="color:darkgreen">cargo_subtype</code> variable, so it can be used later for other things. In the HEQS grf for example, this mechanism is used to let the user choose between different capacities of the same vehicle.
|-
| additional_text
| All
| Yes, only
| String
| Additional text to show in the purchase list.
|-
| colour_mapping
| All
| Yes, unless <code style="color:darkgreen">purchase_colour_mapping</code> is set separately
| Recolour sprite number
|
With this callback, you can use a different recolour sprite instead of the standard 1cc / 2cc company colour remappings. See [[NML:List of default colour translation palettes|here]] for a list of default palettes. See the [[NML:Builtin functions|builtin function]] <code style="color:darkgreen">reserve_sprites()</code> for info on how to allocate your own sprite. For performance, the result is cached and only updated if the <code style="color:darkgreen"> every_32_days</code> callback requires so. Add CB_RESULT_COLOUR_MAPPING_ADD_CC to the result to add the company colour to the sprites, this requires 16 (1cc) or 256 (2cc) sprites in total.
|-
| start_stop
| All
| No
| String or CB_RESULT_NO_TEXT
| Called when starting or stopping a vehicle. Mainly useful to prevent vehicles from leaving the depot unless a certain condition is met. Return CB_RESULT_NO_TEXT to allow or a string (containing an error message) to disallow starting/stopping.
|-
| every_32_days
| All
| No
| bitmask(CB_RESULT_32_DAYS_XXX, ...)
| Called every 32 days. Set CB_RESULT_32_DAYS_TRIGGER in the bitmask to trigger TRIGGER_VEHICLE_32_CALLBACK. Set CB_RESULT_32_DAYS_COLOUR_MAPPING in the bitmask to update the colour mapping by re-running the <code style="color:darkgreen">colour_mapping</code> callback.
|-
| sound_effect
| All
| No
| SOUND_XXX, sound("sound.wav"), import_sound(grfid, number) or CB_RESULT_NO_SOUND
|
Called to play various vehicle sounds. <code style="color:darkgreen">extra_callback_info1</code> contains the sound event, see the [[#Sound events|table]] below. Return SOUND_XXX (see [[NML:List_of_sound_effects|here]]) to return a default sound. <code style="color:darkgreen">sound("soundfile")</code> imports a sound from a .wav file. <code style="color:darkgreen">import_sound(grfid, number)</code> imports a sound from another grf. A failed (or not implemented) callback will cause the default sound to be played. Return CB_RESULT_NO_SOUND to play no sound at all.
|-
| articulated_part
| Trains, Road Vehicles
| Yes (no separate callback)
| Vehicle ID, or CB_RESULT_NO_MORE_ARTICULATED_PARTS
| With this callback, you can add articulated parts (e.g. tenders) to your vehicle. Called repeatedly, until CB_RESULT_NO_MORE_ARTICULATED_PARTS is returned. After each call, the returned vehicleID is added to your vehicle. <code style="color:darkgreen">extra_callback_info1</code> contains 1 during the first call, 2 during the second, etc. Note that callback may be called from the purchase list, using vehicle variables is not possible. Or CB_RESULT_REVERSED_VEHICLE to the returned vehicle ID to display the vehicle backwards.

For NML 0.2 and lower the vehicle ID of the articulated part must be in the range 0 .. 127.
|-
| can_attach_wagon
| Trains
| No
| String or CB_RESULT_ATTACH_XXX
| Called when a wagon is being attached, to allow or disallow attaching. This callback has to be defined at the engine. However, variables in the <code style="color:darkgreen">SELF</code> scope refer to the wagon being attached, the <code style="color:darkgreen">PARENT</code> scope refers to the engine that the wagon is being attached to. Return a string to disallow with the string as error message. Return CB_RESULT_ATTACH_DISALLOW to disallow with standard message ("incompatible railtypes"), CB_RESULT_ATTACH_ALLOW to allow or CB_RESULT_ATTACH_ALLOW_IF_RAILTYPES to allow if the railtypes match (default).
|-
| refit_cost
| {{ottdp|1.2|no|ottdrev=r23089}} All
| Yes
| -8192 .. 8191 as refit cost. Add <code style="color:darkgreen">CB_RESULT_AUTOREFIT</code> if you want to allow autorefit.
| When returning a negative value, encode the cost as (cost & <code style="color:darkgreen">CB_RESULT_REFIT_COST_MASK</code>) before (possibly) adding <code style="color:darkgreen">CB_RESULT_AUTOREFIT</code>. To allow autorefitting, the corresponding bit in the <code style="color:darkgreen">misc_flags</code> must be set as well. Variable <code style="color:darkgreen">extra_callback_info1</code> contains information about the target cargo type in the format 0xccccsstt, with tt being the new cargo type, ss the new cargo subtype (see <code style="color:darkgreen">cargo_subtype_text</code>-callback) and cccc a bitmask of the [[NML:Cargos#Cargo_classes|cargo classes]] of the target cargo type. Note that this callback may also be called when the vehicle does not exist yet, so the available variables are limited.
|}

The following callbacks all have an equivalent property. The property description applies here also, except where otherwise noted.

{| class="t"
! Name
! Available for
! In purchase menu?
! comment
|-
| loading_speed
| All
| No
|
|-
| speed
| All
| Yes, unless <code style="color:darkgreen">purchase_speed</code> is set separately
| Units are not (yet) available
|-
| cost_factor
| All
| Yes, only
|
|-
| running_cost_factor
| All
| Yes, unless <code style="color:darkgreen">purchase_running_cost_factor</code> is set separately
|
|-
| cargo_age_period
| All
| No
|
|-
| cargo_capacity
| All except aircraft
| Yes, unless <code style="color:darkgreen">purchase_cargo_capacity</code> is set separately
|
|-
| passenger_capacity
| Aircraft
| Yes, unless <code style="color:darkgreen">purchase_passenger_capacity</code> is set separately
|
|-
| mail_capacity
| Aircraft
| Yes, unless <code style="color:darkgreen">purchase_mail_capacity</code> is set separately
|
|-
| range
| Aircraft
| Yes, unless <code style="color:darkgreen">purchase_range</code> is set separately
|
|-
| visual_effect_and_powered
| Trains
| No
|
|-
| visual_effect
| Road Vehicles, Ships
| No
|
|-
| power
| Trains, Road Vehicles
| Yes, unless <code style="color:darkgreen">purchase_power</code> is set separately
| Units are not (yet) available
|-
| weight
| Trains, Road Vehicles
| Yes, unless <code style="color:darkgreen">purchase_weight</code> is set separately
| Units are not (yet) available
|-
| length
| Trains, Road vehicles
| No
|
|-
| tractive_effort_coefficient
| Trains, Road Vehicles
| Yes, unless <code style="color:darkgreen">purchase_tractive_effort_coefficient</code> is set separately
| Value range is 0 .. 255 instead of 0 .. 1.
|-
| bitmask_vehicle_info
| Trains
| No
|
|}

===Sprites in GUI===
{{ottdp|1.2|no|ottdrev=r23080}} Since OpenTTD r23080 you can use variable <code style="color:darkgreen">extra_callback_info1</code> to display different sprites in the GUI and on the map. Currently these cases are available:
{| |-
! Lowest byte of extra_callback_info1 !! Meaning
|-
| 0x00 || Vehicle is drawn in a viewport, i.e. on the map.
|-
| 0x01..0x0F || reserved
|-
| 0x10 || Vehicle is drawn in the depot GUI. <ref>OpenTTD also uses this value with the purchase-list chain (cargotype FF) to determine the gridsize in ship and aircraft depots.</ref>
|-
| 0x11 || Vehicle is drawn in the vehicle details GUI. (This includes the refit GUI.)
|-
| 0x12 || Vehicle is drawn in the vehicle list.
|-
| 0x13..0x1F || reserved for other future GUIs.
|-
| 0x20 || Vehicle is drawn in the purchase list. (This includes the autoreplace GUI.)
|-
| 0x21 || Vehicle is drawn in the exclusive preview GUI or in the advertisement news.
|-
| 0x22..0x2F || reserved for other future GUIs with non-purchased vehicles.
|-
| 0x30..0xFF || reserved
|}
<references/>
The other bytes of variable <code style="color:darkgreen">extra_callback_info1</code> are reserved, and must be masked.
The cases 0x20..0x2F are called using the <code style="color:darkgreen">purchase</code>-callback, the other cases are called for the <code style="color:darkgreen">default</code>- or cargo-specific callbacks. Exception is the the special depot-gridsize call, which uses the <code style="color:darkgreen">purchase</code>-callback.

===Sound events===

{| class="t"
! Event
! Description
|-
| SOUND_EVENT_START
| Vehicle leaves station or depot, plane takes off
|-
| SOUND_EVENT_TUNNEL
| Vehicle enters tunnel
|-
| SOUND_EVENT_BREAKDOWN
| Vehicle breaks down (not for planes)
|-
| SOUND_EVENT_RUNNING
| Once per engine tick, but no more than once per vehicle motion
|-
| SOUND_EVENT_TOUCHDOWN
| Aircraft touches down
|-
| SOUND_EVENT_VISUAL_EFFECT
| Visual effect is generated (steam plume, diesel smoke, electric spark)
|-
| SOUND_EVENT_RUNNING_16
| Every 16 engine ticks if in motion
|-
| SOUND_EVENT_STOPPED
| Every 16 engine ticks if stopped
|-
| SOUND_EVENT_LOAD_UNLOAD
| Consist loads or unloads cargo
|}