We believe today that collision avoidance systems can appreciably reduce the number and seriousness of rear-end collisions.The mode of operation of a non - cooperative collision avoidance system is shown. Demands on the radar distance measurement system are described, e. g. questions of radar pulse mode, antenna diagram and choice of frequency.The decisive problem as regards evaluation of the radar echo is the reliable separation of desired and undesired signals. The presented technique uses a time magnification process followed by discrimination according to amplitude, pattern and echo jumps. In addition, there is a radar range limitation which is dependent on speed and steering angle. With experimental vehicles - equipped with the collision avoidance system - over 100 000 km have been covered. The results were very encouraging.