Adaptive cruise control builds on the functionalities of the cruise control system and within certain system limits, maintains the driver-selected comfort spacing from the vehicle in front automatically. The system uses a special radar sensor to measure the distance to the vehicle ahead. If the distance is too small, the system reduces speed moderately by easing the throttle or automatically applying the brakes, up to approximately 25% of maximum vehicle deceleration. Once the road ahead is clear again, adaptive cruise control accelerates the car up to the previously set speed. If the braking process activated by the adaptive cruise control does not decelerate the vehicle sufficiently, an acoustic signal is triggered immediately to warn the driver to intervene manually.
Adaptive cruise control does not react to stationary objects or approaching vehicles. It should not be used on winding roads or in adverse weather conditions such as fog, ice or heavy rain.