Rear collision warning is a function that helps drivers to avoid being hit from behind by a moving vehicle. For vehicles designed with this system, it is immediately activated as you turn on the engine. This system also warns drivers behind your car about possible to rear-end collisions by constantly flashing your direction indicators.  While driving and the system detects your vehicle might be hit from behind, the tensioners will tension the front seat belts and then immediately activate the vehicle’s safety system.  The rear collision warning function might activate the brakes to reduce the vehicle's speed during the collision, so it drives at a safe speed.