In the proposed systems, it is applied by the technology of Wireless Access in Vehicular Environment/Dedicated Short Range Communication (WAVE/DSRC) combining radars installed against the intersection scanning the surroundings and Global Positioning System (GPS) of vehicles to access vehicular speed, latitude, longitude, direction, and other information immediately. The above information will be gathered into DSRC On-Board Equipment (OBE) of the vehicle around the intersection. Meanwhile, it will provide real-time transverse alerts to the vehicles. In this paper, based on theoretical analysis and field trial, it is revealed that the proposed system can warn the driver efficiency, improve traffic safety, and avoid unnecessary false alarms.