Safety of the distance between vehicles is judged by monitoring whether or not an object other than a front road surface, namely, a preceding vehicle, exists in a predetermined area of the front road surface which is recognized by a picture processing unit used as a sensor for recognizing traffic states...http://www.google.com/patents/US5612686?utm_source=gb-gplus-sharePatent US5612686 - Method and an apparatus for monitoring the environment around a vehicle and an operation support system using the same
