NML:Vehicles

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Props, Vars and CBs

Properties common to all vehicle types

property value range available for
articulated
vehicle 		comment
name (string) yes for example string(STR_NAME_HEREFORD_TRAM)
climates_available bitmask(CLIMATE_XXX, CLIMATE_YYY, ...) set to NO_CLIMATE XXX = [TEMPERATE | ARCTIC | TROPICAL | TOYLAND], alternatively NO_CLIMATE or ALL_CLIMATES. To make a vehicle available in all climates except toyland you could use: ALL_CLIMATES & ~bitmask(CLIMATE_TOYLAND).
introduction_date date(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.
model_life 0 ... 254 (years) or VEHICLE_NEVER_EXPIRES no

Number of years a model is "supported" by the manufacturer, see below.

retire_early -128 ... 127 (years) no

Retire the vehicle (make it unavailable in the purchase menu) this many years before reliability starts dropping, see below. May be negative.

vehicle_life 0 ... 255 (years) no Life length of an individual vehicle, before it is considered too old and in need of replacement.
reliability_decay 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
refittable_cargo_classes

bit set of cargo classes

yes for example: bitmask(CC_BULK, CC_COVERED)
non_refittable_cargo_classes

bit set of cargo classes

yes for example: bitmask(CC_OVERSIZED, CC_SPECIAL)
refittable_cargo_types 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.
cargo_allow_refit Array of cargo labels from the cargotable Yes Supported by OpenTTD 1.2 (r23291)1.2 Not supported by TTDPatch A list of cargo types to allow refitting to, irrespective of cargo classes. Example: [COAL, IORE]
cargo_disallow_refit Array of cargo labels from the cargotable Yes Supported by OpenTTD 1.2 (r23291)1.2 Not supported by TTDPatch A list of cargo types to disallow refitting to, irrespective of cargo classes. Example: [MAIL]
loading_speed 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.
cost_factor 0 ... 255 Set to 0 multiplier to the base purchase cost
running_cost_factor 0 ... 255 Set to 0 multiplier to the base running costs
cargo_age_period 0 ... 65535 yes

Supported by OpenTTD 1.2 (r22713)1.2 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

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.

phase duration reliability
1 7 to 38 months increases from 48-73% to 75-100%
2 model_life - 8 years stays constant at peak, 75-100%
3 10 to 20.5 years decreases from peak to 25-50%

If model_life is set to VEHICLE_NEVER_EXPIRES, 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 retire_early 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 sort(FEAT_TRAINS, [D, B, A]); the final sorting will be this: C D B A E

Train properties

property value range available for
articulated
vehicle 		comment
sprite_id SPRITE_ID_NEW_TRAIN yes Set this property to enable new graphics
speed 0 ... 65000 (float, speed units) no Max speed for engines, speed limit for wagons
misc_flags bitmask(TRAIN_FLAG_XXX, ...) FLIP should not be set, TILT and MU the same value XXX=[TILT | 2CC | MU | FLIP | AUTOREFIT] which allows the train to enjoy the tilt bonus, use the 2nd company colour, act as a multiple unit (used for livery selection only) or allow the vehicle to be flipped (reversed) in the depot
refit_cost 0 ... 255 yes in 50% units of the purchase price cost base
callback_flags bitmask(VEH_CBF_XXX, ...) yes

Do not set this, unless you use old-style callbacks.

track_type 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 track_type to RAIL and make sure that you set engine_class to ENGINE_CLASS_ELECTRIC.
ai_special_flag [AI_FLAG_PASSENGER | AI_FLAG_CARGO] no Set to AI_FLAG_PASSENGER to tell computer players that it's an engine that should only be used for passenger service.
power 0 ... 65000 hp (float, power units) Set to 0
running_cost_base RUNNING_COST_XXX Set to RUNNING_COST_NONE XXX = [STEAM | DIESEL | ELECTRIC | ROADVEH | NONE]
dual_headed [0 | 1] Set to 0 for all parts of an articulated vehicle 1 = dual_headed, otherwise normal engine
default_cargo_type An identifier from the 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 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 cargo_capacity callback to avoid this effect.
weight 0 .. 1279 ton (float, mass units) Set to 0
ai_engine_rank 0 ... 255 no TTDPatch only: Higher values make the engine for the TTDPatch AI more attractive
engine_class ENGINE_CLASS_XXX no XXX=[STEAM | DIESEL | ELECTRIC | MONORAIL | MAGLEV]
extra_power_per_wagon 0 ... 65000 hp (float, power units) Set to 0 Only wagons with a livery override for this engine will add power
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.
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.
visual_effect_and_powered visual_effect_and_powered(VISUAL_EFFECT_XXX, offset, ENABLE_WAGON_POWER or DISABLE_WAGON_POWER) yes XXX=[DEFAULT | STEAM | DIESEL | ELECTRIC | DISABLE], it is the type of the visual effect you want for this vehicle. Default means "take from engine_class property". 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.
extra_weight_per_wagon 0 ... 255 ton (float, mass units) Set to 0 Adds extra weight for powered wagons, see extra_power_per_wagon
bitmask_vehicle_info 8-bit bitmask yes

Used for obtaining bitmask_consist_info

Road vehicle properties

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 The following flags are defined: ROADVEH_FLAG_TRAM, ROADVEH_FLAG_2CC, ROADVEH_FLAG_AUTOREFIT. Use 0 if you don't want to set any of these flags.
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 old-style callbacks.

running_cost_base RUNNING_COST_XXX set to RUNNING_COST_NONE XXX = [STEAM | DIESEL | ELECTRIC | ROADVEH | NONE]
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.
default_cargo_type An identifier from the 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 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 cargo_capacity callback to avoid this effect.
sound_effect SOUND_XXX no

See available sound effects.

visual_effect visual_effect(VISUAL_EFFECT_XXX, offset) yes XXX=[DEFAULT | STEAM | DIESEL | ELECTRIC | DISABLE], it is the type of the visual effect you want for this vehicle. 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.
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

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_2CC, SHIP_FLAG_AUTOREFIT) Bitmask with two possible flags, set to 0 to disable
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 old-style callbacks.

is_refittable [0 | 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.
default_cargo_type An identifier from the 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 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 sound effects.

ocean_speed_fraction 0 ... 1 (float)

Supported by OpenTTD 1.2 (r22639)1.2 fraction of base speed on ocean tiles (default: 1)

canal_speed_fraction 0 ... 1 (float)

Supported by OpenTTD 1.2 (r22639)1.2 fraction of base speed on canal tiles (default: 1)

visual_effect visual_effect(VISUAL_EFFECT_XXX, offset) XXX=[DEFAULT | STEAM | DIESEL | ELECTRIC | 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

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 Supported by OpenTTD 1.2 (r23504)1.2 Not supported by TTDPatch 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 two possible flags, set to 0 to disable both
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 old-style callbacks.

is_helicopter AIRCRAFT_TYPE_XXX XXX=[NORMAL | HELICOPTER]
is_large AIRCRAFT_SIZE_XXX XXX=[SMALL | LARGE]. Set to AIRCRAFT_SIZE_SMALL for helicopters.
acceleration 0 ... 255 In arbitrary units
passenger_capacity 0 ... 65536 Capacity for the passenger compartment. See also the notes at mail_capacity 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 passenger_capacity and mail_capacity callbacks.
sound_effect SOUND_XXX

See available 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

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

cargo classes

most_common_refit

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 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, PLAYERTYPE_AI, PLAYERTYPE_HUMAN_IN_AI (human managing AI company) or 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 here for possible values.

company_colour2 COLOUR_XXX Yes

Same as company_colour1, if no 2nd company colour is chosen. Refer to the table 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 or 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 curve_invo_prev_cur + curv_info_cur_next.
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 builtin function vehicle_curv_info() instead to make comparisons. curv_info == vehicle_curv_info(a, b) is equivalent to (curv_info_prev_cur == a) && (curv_info_cur_next == b), 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 cargo class Yes, for the default cargo class of the currently transported cargo
vehicle_is_available [0 | 1] Yes Value is 1 if the vehicle is available on the open market
vehicle_is_testing [0 | 1] Yes Value is 1 if the vehicle is currently being tested
vehicle_is_offered [0 | 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 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 cargo_subtype_text callback.
vehicle_is_powered [0 | 1] No Vehicle provides power and is on the correct track type
vehicle_is_not_powered [0 | 1] No Vehicle is either on a wrong track type or it doesn't provide power at all
vehicle_is_potentially_powered [0 | 1] No Vehicle provides power, if it is on a suitable track type
vehicle_is_reversed [0 | 1] No Value is 1 if the vehicle has reversed an odd number of times
built_during_preview [0 | 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 Random switch)

random_bits 0 ... 255 No

Random data that can be used to randomize certain descisions. (see Random switch)

grfid 0 ... 0xFFFFFFFF No

GRFID that defined the graphics-block for this vehicle. To compare this with other grfids, use the builtin function str2number() to convert the other GRFID to a number as well.

vehicle_type_id 0 ... 65535 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 grfid as well.
vehicle_is_hidden [0 | 1] No Value is 1 if the vehicle is hidden in a depot or tunnel.
vehicle_is_stopped [0 | 1] No Value is 1 if the vehicle is stopped, or if it is braking for a stop (trains only).
vehicle_is_crashed [0 | 1] No Value is 1 if the vehicle has crashed.
vehicle_is_broken [0 | 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 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 | 1] No Value is 1 if the vehicle is inside a depot

Variables that require an argument

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.


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 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 default callback is used instead. Cargo-specific graphics callbacks are never called from the purchase menu, refer to the purchase callback below instead.

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

Name Available for In purchase menu? value range comment
default All Yes, unless purchase is set separately Sprite group 'Normal' vehicle graphics, if no cargo-specific graphics apply.
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 dual_headed 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. )
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 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 cargo_subtype 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 cargo_subtype 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 purchase_colour_mapping 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 here for a list of default palettes. See the builtin function reserve_sprites() for info on how to allocate your own sprite. For performance, the result is cached and only updated if the every_32_days 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 colour_mapping 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. extra_callback_info1 contains the sound event, see the table below. Return SOUND_XXX (see here) to return a default sound. sound("soundfile") imports a sound from a .wav file. import_sound(grfid, number) 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. extra_callback_info1 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 SELF scope refer to the wagon being attached, the PARENT 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).

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

Name Available for In purchase menu? comment
loading_speed All No
speed All Yes, unless purchase_speed is set separately Units are not (yet) available
cost_factor All Yes, only
running_cost_factor All Yes, unless purchase_running_cost_factor is set separately
refit_cost Supported by OpenTTD 1.2 (r23089)1.2 Not supported by TTDPatch All Yes 0 .. 16377 as refit cost. Add CB_RESULT_AUTOREFIT if you want to allow autorefit.
cargo_age_period All No
cargo_capacity All except aircraft Yes, unless purchase_cargo_capacity is set separately
passenger_capacity Aircraft Yes, unless purchase_passenger_capacity is set separately
mail_capacity Aircraft Yes, unless purchase_mail_capacity is set separately
range Aircraft Yes, unless purchase_range is set separately
visual_effect_and_powered Trains No
visual_effect Road Vehicles, Ships No
power Trains, Road Vehicles Yes, unless purchase_power is set separately Units are not (yet) available
weight Trains, Road Vehicles Yes, unless purchase_weight is set separately Units are not (yet) available
length Trains, Road vehicles No
tractive_effort_coefficient Trains, Road Vehicles Yes, unless purchase_tractive_effort_coefficient is set separately Value range is 0 .. 255 instead of 0 .. 1.
bitmask_vehicle_info Trains No

Sound events

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
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