A driver assistance system that uses probability reasoning to recognize a vehicle's environment using information such as the presence of other vehicles, locations, distances and so on, provided by visual sensors is presented in this paper. The prototype system, which is designed to help drivers overtake safely on an express-way, consists of a vehicle detector, a lane detector and an environment recognizer. Firstly, the system detects other vehicles and lanes on the road. Next, it estimates the distance, the relative speed and the location (lane) of the vehicles. On the basis of this information, the system will judge if it is SAFE or NOT-SAFE to overtake.
