Vehicles will be in the next future equipped with V2V telecommunication means to exchange data, such as the presence of an obstacle on the road, or an emergency braking notification. Vehicles are also more and more equipped with perception systems (cameras, laser scanners, radars) that enable them to explore the immediate environment, including other vehicles. We propose in this paper an on-board optical vehicle identification system to enable telecom and perception systems to cooperate. The optical identification identifies which vehicle, in the scene captured by the perception system, is sending information via telecom. ©2007 IEEE.