About one third of all car accidents are due to collisions with other
vehicles or objects on the road. In almost 50 percent of such accidents, the
driver doesn’t brake at all or, in another 20 percent, is much too hesitant.
Many of these crashes will in future be prevented by Predictive Safety
Systems, electronic systems that actively attempt to prevent cars crashing.
Robert Bosch GmbH, the world’s second largest supplier to the automotive
industry, intends to combine Antilock Braking System (ABS), Electronic Stability
Program (ESP) and Hydraulic Brake Assistant (HBA) with the radar sensor of Adaptive Cruise Control (ACC) and, in future, also video sensors.
"Based on the information received by the sensors on distance, relative speed
and size of preceding vehicles, the systems are capable of activating the safety
functions even before the imminent crash", says Dr. Bernd-Josef Schäfer, Vice
President, Business Unit Driver Assistance Systems, Bosch Automotive Electronics
“Vehicle developers can further improve the effectiveness of current active
and passive safety systems if they include information about the vehicle's
environment,” he says.
Bosch plans to develop the Predictive Safety Systems in three stages.
Stage 1 - the system prepares the brake
system for a possible emergency braking
In situations where there is the threat of an accident, the Predictive Safety
Systems prepares for it by building up brake pressure, brings the brake pads
into very light contact with the brake discs and modifies the hydraulic brake
The result is that the driver gains important fractions of a second until the
full braking effect is achieved. If he then undertakes emergency braking, he
gets the fastest possible braking action with the maximum deceleration and thus
the shortest stopping distance. If he does not need to brake, these preparatory
measures are withdrawn.
Even if there is an accident, the system can reduce the side-effects and save
lives. A typical situation which can lead to an accident is when a much slower
vehicle moves out into the lane in which you are driving on the motorway. If you
are driving at 140 km/h and the vehicle in front moves into your lane 40 metres
ahead of you travelling at only 80 km/h, the Predictive Safety System prepares
for emergency braking in only a fifth of a second – before you have even noticed
the slow-moving obstacle. In the event of emergency braking, the driver benefits
from the more rapid operation of the braking system, enabling him to avoid an
accident: without the Predictive Safety System there would have been a serious
Bosch is planning the series introduction of the first generation of the
Predictive Safety System for 2005.
Stage 2 - Warning where there is the danger
of colliding with the vehicle in front
The second generation of the Predictive Safety System does not only prepare
the braking system, it also gives a timely warning to the driver about dangerous
traffic situations, helping in many cases to prevent accidents.
To do this it triggers a short, sharp operation of the brakes. Studies of
drivers have shown that a sudden braking impulse is the best way of drawing the
driver's attention to what is happening on the road; drivers react directly to
the warning. The system can also warn the driver by means of visual or sound
signals, or by a brief tightening of the normally loosely-fastened safety belt.
In the case outlined above where a vehicle moves into the lane in front of
you, the extended Predictive Safety System prepares for emergency braking in
only a fifth of a second. The difference from the first generation of the safety
system is that the driver is also given a warning if he does not change course
or brake within the next third of a second.
In this case, the driver can still avoid a crash by moving out of the lane.
If he only brakes, he can at least considerably reduce the speed of his vehicle.
Series launch of the 2nd generation of the Predictive Safety System with the
warning function is planned by Bosch for 2006.
Stage 3 - Emergency braking in unavoidable
The third developmental stage of the Predictive Safety System will not only
recognize an unavoidable collision with a vehicle in front, but the system will
in this instance also trigger automatic emergency braking with maximum vehicle
This will reduce the severity of an accident when the driver has failed to
react at all to the previous warnings, or has reacted inadequately.
Automatic control of vehicle function demands a very high level of certainty
in the recognition of objects and the assessment of accident risk. In order to
be able to reliably recognize that a collision is inevitable, further systems –
such as video sensors – will have to support radar sensors. It will also be
necessary to create the legal basis for the use of such systems for traffic on
Video Cameras and Lane
The video camera developed by Bosch is fitted behind the windscreen, situated
within the area of the screen swept by the wiper blades so that its field of
vision is kept free of dirt and water drops.
Bosch uses CMOS (Complementary Metal Oxide Semiconductor) semiconductor
technology for the image sensor. The incident light is converted into electrical
impulses by the sensor's image elements – the pixels. The impulses are then
converted in the analogue-digital conversion into information on the level of
brightness of each individual pixel. The CMOS sensor can clearly distinguish
very bright sources of light from the background and present the overall image
This means that the camera is ideally suited for use in vehicles.
It "sees" the area in front of the vehicle and when combined with a powerful
computer and good-quality image processing, can support the driver in many
For lane recognition, for example, the video camera detects the course of the
road or lane in front and the road or lane boundaries. A fast computer
simultaneously processes the image signals captured by the camera. The computer
uses special software developed by Bosch which makes use of data derived from
computer modelling – for example, on typical courses of roads or the layout of
If the system detects that the vehicle is unintentionally drifting out of the
lane or off the road, it sends a warning to the driver. Depending on the
application, the warning may be given by sound or by vibrations sent to the
driver's seat or the steering wheel.
A lane-holding assistance function is being developed for the next generation
of the system. Precisely targeted steering impulses support the driver when the
vehicle is in danger of unintentionally leaving the road. However, the driver
can intervene, override the system support or even switch off the system
In addition to lane recognition and lane-holding, Bosch's development
engineers are assigning further assistance functions to the front-mounted video
camera. For example, linking in the video system is seen as absolutely necessary
for future extensions of the ACC system which currently uses a radar sensor.