This paper presents a method I for tracking and segmenting vehicles in a traffic scene. The approach is based on a frame to frame segmentation followed by a tracking process. As opposed to usual segmentation methods, our method feedbacks segmentation with tracking information for improving results. Several facilities are provided for traffic monitoring such as vehicles trajectories surveillance, segmentation of vehicle shape, measuring the mean velocity of the traffic, counting the vehicles that are moving on the lanes of a road or a motorway, counting the vehicles that stop at a junction and detection of events such as a vehicle stops on a road or a possible accident. Key Words : Region tracking, motion analysis, motion segmentation, traffic monitoring, vehicle surveillance