This paper deals with the issue of using multi-cameras for road traffic monitoring. The aim is to remove the classic monocular ambiguities and to retrieve the objects' height. An efficient and simple calibration method is introduced. It has the particularity to be connected to the geometry constraints of the road. The method relies on projective geometry and uses the structure of the plane at infinity. In a second stage, a high speed matching procedure is introduced. It is based on an altitude planar decomposition of the road scene. The method naturally achieves two tasks due to altitudes sampling. Match and reconstruction become simultaneous. Finally, experimental results are presented.