RCW activates automatically whenever the engine is started and it cannot be switched off.
The RCW can warn the driver in a vehicle approaching from behind that a collision is imminent by rapidly flashing the direction indicators.
If with a vehicle speed below 30 km/h (20 mph) the RCW function detects that the driver's vehicle is in danger of being hit from behind, the seatbelt tensioners may tension the front seatbelts and the Whiplash Protection System safety system is activated.
Immediately before the collision, RCW may also activate the foot brake in order to reduce the forward acceleration of the driver's vehicle during the collision. However, this can only happen if the driver’s vehicle is stationary. The foot brake releases immediately if the accelerator pedal is depressed.
In certain cases the RCW may have difficulty helping the driver in the event of a collision risk. This can be for example:
- in slippery conditions when the Electronic stability control intervenes
- if the vehicle approaching from the rear is detected too late
- if the vehicle approaching from the rear changes lane at the last moment
- if the vehicle approaching from the rear has a speed exceeding 80 km/h (50 mph).
In certain markets, RCW does not give a warning with the direction indicators due to local traffic regulations - in such cases, this part of the function is deactivated.
Warning with the direction indicators for Rear Collision Warning deactivates if the warning distance for collision warning is set to the lowest level "Later" (see section "Set warning distance for City Safety").
The seat belt pre-tensioning and braking functions are, however, still active.