This paper details a vehicle detection and localization algorithm from a single perspective view. A video camera, embedded i n a car, provides a grey scale image of a lead car. This lead vehicle is equipped with three visual marks to make easier low and high level processes. The algorithm is designed for real time implementation. It is conceived f r om a direct 3D localization method c oupled with a tracking method b ased on a rigidity criteria of the trajectories of N points. The processes are implemented n a specialized h a r dware a r chitecture to satisfy real time constraints.