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Precrash Safety

Basic Description

Precrash Safety Systems warn the driver of a possible crash ahead and then take various actions to improve the safety of the car if the driver does not immediately act to prevent the collision. These systems have been shown in real world tests to reduce the force at impact by up to 40%.

Head-on car collision illustrationPrecrash Safety Systems use radar, laser and/or image sensors to detect if a crash is imminent. If the system detects a possible collision, it will alert the driver with visual and/or audio signals to the impending crash. If the driver does not make a move to slow the car or is going too fast to brake in time, precrash safety systems generally tighten the seatbelts and increase the brake pressure to prepare the brakes for better performance. Some systems will take additional measures, such as closing the windows and sunroof, inflating air chambers in the seats, positioning the passenger seat in a more upright and safe position, and raising the rear backseat headrests.

Nissan has introduced a novel "Predictive Forward Collision Warning" system capable of detecting a vehicle two cars ahead in order to help prevent pileup collisions. The system uses radar sensors that are able to detect the second vehicle ahead by extending the radar's range underneath the vehicle directly in front. When the system detects potential risks, it informs the driver through the dashboard display, an audible warning and tightening the seat belt. If the driver has activated the Forward Emergency Braking system, upward pressure is applied to the accelerator pedal and braking is applied. This system is available on the 2014 Infinity Q50.

Radar, Laser and/or image sensors, vehicle speed sensor, yaw sensor, acceleration sensor, accelerator pedal position, brake pedal position, headrest position, seat position
Throttle, brakes, window control, power seats, headrest control, seatbelt tensioner
Data Communications
Control Area Network (CAN) or FlexRay
Denso, Honda, Lexus, Mercedes-Benz, Nissan, Toyota, Volkswagen
For More Information
[1] Collision Avoidance System, Wikipedia.
[2] Nissan Predictive Forward Collision,, YouTube, Dec. 1, 2011.
[3] Reward 2010-Mercedes Benz Presafe, European New Car Assessment Program,
[4] Mercedes Benz S-Class, Pre-Safe Braking, YouTube, May 12, 2007.
[5] Honda Collision Mitigation Braking System, YouTube, Sep. 27, 2010.
[6] Toyota Precollision System, YouTube, Apr. 21, 2009.
[7] 2010 Prius Pre-Collision System Test, YouTube, May 14, 2010.
[8] Advanced Pre-Collision System: The 2013 Lexus LS Innovation Series, YouTube, Oct. 29, 2012.
[9] Avalon How-To: Pre-Collision System (PCS), YouTube, Jan. 28, 2013.