This is how active safety systems work and how they can save you from an accident.
Adaptive cruise control is a convenience that uses the car's radar and camera modules to alter the set cruising speed if it detects a slower vehicle ahead. When adaptive cruise control is engaged, the car will maintain a specific distance from the car in front; many cars come with three set options for the following distance. Some advanced versions of the feature will also bring the vehicle to a complete stop if the car ahead stops and will then start to back up when traffic begins to move. Such a feature is quite handy and reduces driver fatigue by allowing the use of cruise control in dense-traffic driving scenarios.