How Pre-Collision Systems Work

Pre-collision systems are active safety systems designed for automobiles to avoid or minimize the extent of damage in the event of a crash. These systems evaluate the position of the driver and his environment constantly to predict a likely accident and take steps in advance to minimize injury. They may either beef up the active safety systems in the car or even brake automatically to bring the car to a halt.


Crash safety systems started in the 1950’s with the advent of seat belts. As the number of cars on the road and their speed raised over the years, it called for improved safety features. By the end of the 20th century, crash tests became mandatory for all vehicles. This resulted in passive safety features like impact beams, crumble zones and, active features like airbags, antilock brakes, traction control and brake force distribution. Pre collision systems started finding its way into automobiles by mid-1990s.

Early pre-collision systems used infrared rays to detect the traffic movement. Infrared had limited visibility, which reduced the effectiveness of such systems. Modern systems are radar based, using ultrasound, radio waves or laser so as to monitor the car’s environment constantly. These systems can detect the position, distance and relative velocity of more than one vehicle in front of the car at any time.

Some systems produce an alarm to alert the driver if the radar finds out a potentially hazardous circumstance. Others take over the control of some aspects of the car like braking. They prepare the car for a collision by tightening the seat belts and arranging the seats of the car so that the passengers are aligned to be perfectly protected by the airbags. Some of these systems pre-charge the cars brake so as to improve the response time or even provide additional-braking pressure to bring the car to a halt. Advanced system will automatically brake the car, bringing it to a pause before crashing on to another car.


One of the earliest cars to feature collision detection system was the 2003 Mercedes S-class, which detects emergency maneuvers by the driver and rear rearrange the seating position, radio antenna, sun roof into the safest position. The 2006 S-class had radar based cruise control system that automatically slowed the car down to the pace of the car in front of it without any interference from the part of the driver. The collision mitigation braking system introduced by Honda in 2003, was the first system to brake the car automatically if the driver does not respond to the alert provided and tightening up of the seatbelt.

Toyota has developed a number of pre-crash safety systems including Lane Keep Assist, which alerts the driver and provides small steering input if he accidentally strays over the white line. Other systems employed by Toyota and its luxury wing Lexus include Collision-avoidance Steering Support that up on detecting a possible emergency including collision with pedestrians, adjusts steering ratios, damper stiffness and even provide torque assist to aid any evasive action by the driver.

The manufacturers who currently employ pre-collision braking system in their cars include Acura, Lexus, Infiniti, Mercedes Benz, BMW, Ford, Volvo and Lincoln. Pre collision systems are the latest trend in the automobile safety and more and more manufacturers are using collision detection/avoidance systems in their cars.

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