Precrash Safety System

Pre Crash Safety Systems detect an imminent crash and deploy safety devices such as seat belt pretensioners.

Car manufacturers take care to ensure that their safety systems are effective for occupants of different sizes and for those sitting in different positions. However, the best levels of protection are achieved when the interaction between the occupant and restraint systems are optimised.

Some systems react immediately following or during the crash to optimise occupant safety. For example, they may not directly restrain the occupant but may control the occupant's movement so that the restraint systems work most effectively. Other systems may predict when an accident is about to happen and in a split second prepare the vehicle and its occupants for the crash.

Predicting the accident can be done in a number of ways: vehicle dynamics and driver actions can be can be monitored for panic reactions, or radar sensors can detect obstacles in front of the car.

The actions which the systems take can also vary but, typically, slack will be removed from seatbelts, seating positions may be quickly adjusted to optimise airbags performance and windows shut to prevent ejection. In such cases, the actions taken are reversible in the event that the crash is avoided.