How can serious accidents be prevented? How can technology support drivers? Bosch researchers work intensively on such questions.

One important finding of our accident research is: The earlier an imminent accident is recognized, the more possibilities drivers have to react. Another conclusion was that many drivers are not able to do "all the right things" in the moment of shock. For instance they do not brake quickly enough and consequently reduce the available braking distance.

The solution from Bosch for such situations is PSS – Predictive Safety Systems. The intelligent technology warns drivers in advance, supports them and intervenes in an emergency to reduce the consequences of an accident.

An overview of the Predictive Safety Systems (PSS)
A highly advanced radar system constantly monitors the area in front of the vehicle. The PSS software analyses information from the "electronic eye" and can recognize a dangerous situation at an early stage.

As soon as an accident is likely, effective safety measures are introduced in three stages – faster than any driver could react.

1. The first PSS stage (PBA) prepares the vehicle for an emergency stop to reduce the braking distance to a minimum.

2. If the driver does not detect the danger and react, the technology warns him of the danger using a short, noticeable burst on the brakes and/or acoustic/visual signals and/or a short tug on the seatbelt. This function will be available in a second development stage (PCW).

3. In the third stage, the system will make an emergency stop independently before an unavoidable accident, if the driver does not react on time (PEB).

The future is here already
It may sound like science fiction to some people, but the electronic "guardian angels" from Bosch Predictive Safety Systems will soon improve safety on Europe's roads: The first stage of the system – Predictive Brake Assist (PBA) – will be on the road early this year. The next stage, Predictive Collision Warning (PCW) is almost ready for serial production.

PSS intelligently use the existing safety and convenience systems ABS, ESP®, Hydraulic Brake Assist (HBA) and Adaptive Cruise Control (ACC). By combining and networking these systems, it is possible to recognize accidents in advance and introduce effective counter-measures.

Recognizing danger: high performance sensors
The radar sensor already used in Adaptive Cruise Control to automatically maintain an adequate distance from the vehicle in front can also serve PSS to monitor a distance of 200 meters ahead. The sensor detects vehicles in the same lane and calculates their distance and speed. PSS systems are always active, regardless whether ACC is activated or not.

Ideally preparing a braking maneuver: the Predictive Brake Assist (PBA)
If the sensor detects an accident risk, making an emergency stop probable, the Predictive Brake Assist (PBA) – the first stage of Predictive Safety Systems – prepares the braking system for an emergency stop. It fills the brake circuit in advance, to achieve the required pressure more quickly, and positions the brake lining close to the brake discs, without the driver noticing. The PBA also lowers the tripping level of the Hydraulic Brake Assist. Studies have shown how effective such measures can be: Even in critical driving situations, only a third of all drivers react with an emergency braking maneuver. Most drivers are so hesitant that the Hydraulic Brake Assist is not actuated.

Drivers gain valuable time with the PBA: As soon as they step on the brakes full braking performance is available – around 30 milliseconds earlier. The combination of the driver's reaction and the assistant can significantly shorten braking distances.

Reacting faster: Predictive Collision Warning (PCW)
The second module of the Predictive Safety Systems, Predictive Collision Warning (PCW), additionally warns drivers of critical situations. A short burst on the brakes, a brief tug on the safety belt, and visual and acoustic signals all alert the driver to the imminent danger.

The figures speak for themselves: A study by the Association of German Insurers* shows that almost half of all drivers involved in accidents did not brake at all.* Early warning allows drivers to react faster to the danger of a collision by taking evasive action and/or braking to reduce the impact speed. PCW thereby significantly contributes to avoiding many accidents and reducing the severity of collisions.

* Source: Prof. Langwieder, Association of German Insurers e.V.

Active intervention: the Predictive Emergency Brake (PEB)
If the driver does not react despite all warnings and the system recognizes an unavoidable accident due to the position and speed of the other vehicle, the Predictive Emergency Brake (PEB) is actuated. Until this moment, the driver is the determining party and is merely supported by the safety systems. But from then on, the PEB automatically activates an emergency braking maneuver at maximum strength in view of the imminent collision. The system uses the last chance to reduce the force of an unavoidable collision and minimize injuries.

Maximum safety is required
Since PEB actively intervenes in the driving process, Bosch applies the highest safety standards for object recognition and accident risk assessment. This means that the radar system must be supported by another measuring system, such as video sensors.

CAPS: even safer in future
New electronic systems will contribute to reducing the number of road accidents and the risk of injuries to a minimum. A promising method is combining active and passive safety systems with the predictive driving assistant systems that Bosch is developing in the CAPS program.

Predictive Safety Systems are the first step in this direction. In future, CAPS functions will not only prevent or reduce the impact of collisions in the frontal area, but also provide all vehicles with all-round protection from different types of accidents. Drivers will have active support in dangerous situations that could lead to lateral, rear or multiple collisions or cause the vehicle to roll over.

Development engineers at Bosch are working to make vehicles ever safer for all traffic participants. Our vision is accident-free road traffic.