"Pre-crash Safety System”A pre-crash system is an automobile safety system designed to reduce the severity of an accident. Also known as forward collision warning systems they use radar and sometimes laser sensors to detect an imminent crash. Depending on the system they may warn the driver, pre-charge the brakes, inflate seats for extra support, move the passenger seat, position head rests to avoid whip lash, tension seat belts and automatically apply partial or full braking to minimize impact. Pre Crash Safety Systems detect an imminent crash and deploy safety devices such as seat belt pre-tensioners (devices that control the movement of the seat belt).Lots of 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 optimized.  The pre-crash sensing system uses radar to minimize injury and damage in the event of a collision. It is the world’s first collision-warning and injury-reduction system. Operating at 77 GHz, the millimeter-wave radar and ECU combination is effective at relative velocities up to 200 km/h, over distances up to 150 meters. DENSO’s unit also covers a 20°arc, wider than that of competing systems, giving it a greater range for detecting potential obstacles. Millimeter-wave radar determines an object’s position, distance, and speed; this information goes into a pre-crash safety computer which also takes into account relative velocities, distance, and other factors to determine whether or not a collision can be avoided. If not, it notifies the seatbelt control computer, which tightens up any slack in the seatbelts to maximize the initial restraint on the driver and passengers at the moment of the crash.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.