Automatic distance control builds on the functionalities of the cruise control system by adding a radar sensor to automatically maintain the correct distance from the vehicle in front, within certain system limits. If the car approaches a slower vehicle ahead, the automatic distance control decelerates the car to the same speed in order to maintain the distance set by the driver. If a vehicle pulls into the lane ahead, the car's speed is likewise reduced to match the other vehicle's speed. Once the road ahead is clear again, the car is accelerated back up to the selected cruising speed. In this way, automatic distance control enhances both driving comfort and safety. However, responsibility still ultimately rests with the driver. A radar sensor permanently monitors the area up to 180 metres in front of the car. As well as the distance to any vehicles ahead, the system also measures the rate of approach. If the distance drops below the set safety margin, the automatic distance control makes corrective controls via the engine management and, if necessary, the braking system too. If the required rate of deceleration exceeds 30 percent of the vehicle's maximum deceleration, the driver will be prompted to apply the brakes manually. Even with the automatic distance control activated, the driver is still responsible for monitoring the car's speed and the distance from the vehicle in front. Automatic distance 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.