Rear end collisions during daylight hours are one of the most common vehicle accidents. Studies have shown that in almost a third of these collisions the driver does not hit the brakes, or, if he does with insufficient force! The major reason for this type of accident is lack of concentration by the driver. Now companies such as Bosch are developing technologies to help either prevent or mitigate the consequences of this type of accident.
Predictive emergency braking systems can considerably reduce the incidence of rear end collisions. The basis of the system is first to warn, then assist and, lastly to brake automatically. The initial system developed by the company in 2005 was predictive brake assist, where if the driver brakes then they are applied harder and faster. In 2007 the system was expanded; if a predetermined distance between the vehicle in front is rapidly reduced, the system automatically warns the driver by briefly jerking the brakes. This is known as predictive collision warning.
Future systems take the technology to a new level. A video sensor will support a radar sensor allowing the situation ahead of the vehicle to be interpreted much more quickly and accurately, making two new functions easier:
1. If the driver starts to apply the brakes in a situation that the system deems to be critical, the braking pressure is automatically increased. The aim is to bring the vehicle to a standstill before it hits the obstacle in front. If the accident is unavoidable, maximum deceleration will at least reduce its severity. This is termed target braking.
2. In critical situations, the system autonomously initiates partial braking at a pressure roughly 30 percent of maximum deceleration. This gives the driver more time to react. If an accident is unavoidable, the system triggers maximum deceleration. Research indicates that, in a car being driven by an average driver, the speed of impact will be reduced by 25 to 55 percent. Cutting the speed by half lessens the impact energy by 75 percent, significantly reducing the risk of injury.
Bosch has announced that both of these new systems will go into series production this year in two different models. Bosch estimates that automatic emergency braking could prevent three out of four rear end collisions involving injury.