The authors propose a vehicle ad-hoc network for traffic information service. It allows collecting and analyzing traffic status of large areas without any infrastructure, e.g., probe cars, road side unit, and server. The proposed scheme uses multi-channel and broadcasting technique. Vehicle terminal simply needs the existing navigation systems in vehicles and wireless communication devices for Vehicle-To-Vehicle communication. Communication and networking algorithm is given and experimented on the testbed. It effectively collects accurate traffic information, and is able to provide real-time traffic information propagation by using only Vehicle-To-Vehicle (V2V) communications without infrastructure.