"80% of drivers do not hit the brakes at all before a rear-end collision, or do not use the car's full braking capacity." Dr Werner Struth, Bosch.

IN GERMANY, 15% of all rear-end collisions result in injury and fatalities. So predictive systems that interpret the state of the traffic flow ahead of the vehicle, warn drivers, support them, and finally react automatically can significantly reduce the number of such accidents.

Interpreting more precisely what's happening in front of the vehicles can help driver assistance systems more effectively support the driver.

Video and radar technology combine

At Bosch, our engineers have developed a combination of radar and video for optimum recognition of traffic situations. The functions now feature for the first time in the new Audi A8, as part of the 'pre-sense' package.

The Audi A8 features two long-range radar sensors, which are housed at the left and right of the front bumper. These can detect objects within a beam width of approximately 40 degrees at a distance of up to 250 metres, and can determine their position and speed. The video camera is positioned behind the front windscreen, at the same height as the rear-view mirror.

The advantage of video technology is the high level of information content. The radar signals deliver precise data as to the position and speed of the people, vehicles, or traffic signs captured in the video images.

Warn, support, and then intervene

In a first step, if the predictive emergency braking system detects a potential obstacle, such as a vehicle that is slowing down very fast or coming to a standstill, the brake is primed for the emergency braking that may follow.

This involves the brake control system building up initial pressure, positioning the brake pads closer to the discs, so that they can provide immediate deceleration in the event of a subsequent braking.

If the driver does not react, and the vehicle gets closer, an acoustic warning is given, followed by automatic partial braking, signalled by a brief pull on the brakes.

If the driver still does not react, and if a collision can no longer be prevented, the system brakes automatically at maximum pressure roughly half a second before impact, in order to reduce speed of impact and mitigate the consequences of the accident.

In this way, our system – which is seeing series production for the first time – can help drivers react properly and potentially reduce the level and seriousness of rear-end collisions.