In this paper, the authors describe a vehicle-infrastructure cooperative system called DSSS (Driving Safety Support Systems) used for the prevention of right-turn and left-turn collisions. The research is based on Japan's road system in which vehicles drive on the left-side of the road. The authors describe the development of roadside units (RSU) combining an infrared beacon and a dedicated short range communication (DSRC) beacon, that communicate information of oncoming vehicles detected by an image sensor to on-board units (OBU). The units were tested in field operations conducted in Tochigi prefecture of Japan. Results show that the system gives the caution warning only when necessary and that automobile drivers have given the demonstration units a favorable evaluation.