The centrepiece of the adaptive cruise control is a radar sensor at the front of the vehicle. This sensor uses three radar beams to scan the surroundings every 50 milliseconds ahead of the vehicle, thus monitoring all three lanes of a motorway, for example. In case the radar signals detect a moving vehicle ahead, they are reflected.
A microcomputer then calculates the distance based on the reflected signal and the relative speed of the vehicles in relation to each other. This microcomputer is connected to the other safety systems of the vehicle via the CAN bus. If there is no vehicle ahead that is moving more slowly, the adaptive cruise control functions as a classical cruise control and it maintains the preset speed. Should the system, however, detect a vehicle ahead that is moving more slowly, it reduces the speed by a controlled operation of the engine and brake system. During this operation, no more than 20% of the maximum brake power will be applied. Only the driver can initiate stronger braking manoeuvres. The driver is alerted through visual and acoustic signals about the danger. If the distance to the vehicle ahead exceeds the minimum allowed distance again, the vehicle is accelerated until it reaches the preset speed once more.