191. Crash checker

The crash_checker uses the upon_w watcher operator to trigger a crash interval when a collision event is detected between two physical objects in the simulation.

191.0.1 Start condition

The crash_checker monitors all physical objects in the simulation and raises issues when collisions occur between them.

191.0.2 End condition

The crash_checker creates a zero-time interval for every detected collision. This interval starts and ends in the same simulation step, meaning it ends instantly at the moment of collision without requiring a separate end condition.

191.1 Attributes

The following attributes define the behavior and characteristics of the evaluator.

Checker attribute	Description
Parent object	`physical_object.global_checkers`
Issue category	`sut` or `other`
Issue kind	`collision_in_hybrid_control`, `collision_in_sut_control`, `collision_in_manual_control`
Default severity	error
Trigger condition	Based on `upon_w` watcher

191.2 Configuration parameters

No configuration parameters found.

191.3 Metrics

The following metrics are recorded and tracked by the evaluator.

Metric	Type	Description	Unit
`side`	enum (`front`, `front_left`, `left`, `back_left`, `back`, `back_right`, `right`, `front_right`, `other`)	Side of object on which the collision happened
`other_side`	enum (`front`, `front_left`, `left`, `back_left`, `back`, `back_right`, `right`, `front_right`, `other`)	Side of other object on which the collision happened
`velocity`	speed	Longitudinal velocity at collision, in local coordinate system	kph
`other_velocity`	speed	Longitudinal velocity at collision of the other object, in local coordinate system	kph
`acceleration`	acceleration	Longitudinal acceleration at collision, in local coordinate system	mpsps
`other_acceleration`	acceleration	Longitudinal acceleration of the other object at collision, in local coordinate system	mpsps
`delta_v`	speed	Delta-V between this object and the other object it collided with (kph). Relevant only for a collision between two vehicles. In case one of the objects is not a vehicle, the recorded value is -1kph.	kph
`pdof`	angle	PDOF between this object and the other object it collided with. Relevant only for a collision between two vehicles. If one of the objects is not a vehicle, the recorded value is -999degree.	degree
`pdof_side`	enum (`front`, `rear`, `left`, `right`, `not_applicable`)	PDOF side for this object
`crash_severity`	enum (`S0`, `S1`, `S2`, `S3`, `not_applicable`)	Individual crash severity for this object involved in the collision. For vehicle-to-vehicle collisions, calculated from Delta-V and PDOF side. For vehicle-to-VRU collisions, calculated from the vehicle's speed at impact using VRU thresholds (not_applicable for the VRU). For other collision types, the recorded value is not_applicable.
`other_crash_severity`	enum (`S0`, `S1`, `S2`, `S3`, `not_applicable`)	Individual crash severity for other object involved in the collision. For vehicle-to-vehicle collisions, calculated from Delta-V and PDOF side. For vehicle-to-VRU collisions, calculated from the vehicle's speed at impact using VRU thresholds (not_applicable for the VRU). For other collision types, the recorded value is not_applicable.
`overall_crash_severity`	enum (`S0`, `S1`, `S2`, `S3`, `not_applicable`)	Overall crash severity computed between this_object and other_object. For vehicle-to-vehicle collisions, the higher of the two individual severities. For vehicle-to-VRU collisions, the vehicle's severity at impact. For other collision types, the recorded value is not_applicable.
`other_category`	enum (`car`, `bus`, `truck`, `trailer`, `bicycle`, `motorcycle`, `person`, `animal`, `other`)	Category of the other object

191.4 Log and Error Messages

Output Condition	Description	Default Severity	Action
If the checkers' triggering conditions are met, it warns the user	collision_in_sut_control	Error	Investigate the SUT's behaviour.

191.5 Usage

On each collision, both involved objects receive a zero-time crash interval. An issue is raised only on the object designated as the main collision object (is_main_collision_object).

191.5.1 How to instantiate

The crash checker is built into every physical_object through physical_object.global_checkers and does not require separate declaration per vehicle in the scenario OSC files. It is pre-configured to trigger on every collision event:

extend physical_object.global_checkers:
    checker crash(crash_data) is upon_w(ev: @actor.collision)

191.5.2 Set parameters at instantiation time

The crash checker has no configuration struct and no parameters to set at instantiation time. Metrics such as delta-V, PDOF, and severity are computed automatically in crash_data.

191.5.3 Define and use a custom parameter set

The crash checker has no configuration struct. To customize its behavior, extend global_checkers on the actor scope you want to affect:

191.5.4 Disabling the checker

To disable the checker (all physical objects):

extend physical_object.global_checkers:
    on @start:
        override(crash, run_mode: freeze)

To disable the checker for a specific vehicle subtype (for example, NPCs):

extend npc_vehicle.global_checkers:
    on @start:
        override(crash, run_mode: freeze)

191.5.5 Changing the default SUT collision issue severity:

extend sut:
    keep(collision_severity == warning)

191.5.6 Downgrading or filtering crash issues:

extend physical_object.global_checkers:
    set_issue(target_checker: crash, severity: warning)
extend physical_object.global_checkers:
    set_issue(target_checker: crash, severity: warning,
        condition: it.this_object.is(sut_vehicle) and it.other_object.is(npc_vehicle))

191.6 Additional information

Collision targeting

For compound objects (e.g., truck, trailer), the this_object field identifies the specific part impacted.

Delta-V metrics
- Vehicles: Contains the calculated Delta-V value.
- Non-vehicles: Set to -1kph.
Disabling options
- Global: Disable for all objects
OSC2 code: disable crash globally
```
extend physical_object.global_checkers:
on @start:
    override(crash, run_mode: freeze)
```
- Selective: Disable by object subtypes, for example NPCs
OSC2 code: disable crash for subtype npc vehicles
```
extend npc_vehicle.global_checkers:
on @start:
    override(crash, run_mode: freeze)
```
See Metrics examples for the full examples.

Severity control

Use set_issue() to:

Downgrade all crash issues

OSC2 code: downgrade all crash issues

extend physical_object.global_checkers:
set_issue(target_checker: crash, severity: warning)

See Metrics examples for the full examples.

Conditionally modify severity levels

OSC2 code: conditionally downgrade collision issues

extend physical_object.global_checkers:
set_issue(target_checker: crash, severity: warning,
    # In the context of set_issue(), 'it' refers to the 'data' object of the checker
    condition: it.this_object.is(sut_vehicle) and it.other_object.is(npc_vehicle))

See Metrics examples for the full examples.

Issue classification

Issues are tagged by the controller at impact:
- collision_in_hybrid_control
- collision_in_sut_control
- collision_in_manual_control