For the realization of a safe road traffic environment a wireless communication system which makes an information network between pedestrians and vehicles has been needed. A prototype of pedestrian-to-vehicle communication system was developed by using a cellular phone and a car navigation system equipped with GPS and wireless communication function. By interoperation of 3G wireless network and wireless LAN, it was possible to communicate in a wide area and with little delay time in a local area. The system can exchange the necessary information between pedestrians and vehicles, inform of the location of the ones that have an accident risk, and give an alarm by employing the developed algorithm for estimating the collision risk between each pedestrian and vehicle. The effectiveness of the system was shown by simulation of traffic situations.