A prototype inter-vehicle communication system using infrared rays has been developed and successfully demonstrated. In this study, our efforts have mainly focused on protocol development. For inter-vehicle communication, a very quick transmission cycle, high adaptability to vehicle formation change and high data reliability are required. In this paper, we have proposed new communication protocol which satisfies these requirements. In the experiment, four test vehicles equipped with the prototype system were run on a test track. Actual communication was carried out with vehicles running in various situations successfully and status maps for adjacent vehicles were obtained from the received data.