Optimal control of traffic signals and the sophisticated provision of traffic information to drivers in real time is desired in order to reduce traffic accidents and relieve traffic congestion. To realize these goals, it is essential to collect traffic information. One requirement for a vehicle detector, which is one type of traffic information collection system, is low power consumption and wireless operation. Behind this requirement is the desire to collect traffic information without the need to supply AC power on roads where a commercial power source is unavailable, the importance of aesthetics in urban settings, and conversion to the wireless transmission of detection signals. Further recent considerations are the call for measures to protect the global environment and the utilization of "clean energy" as an environmental measure. This paper describes a practical traffic information collection system in which vehicle detectors are powered by small solar cell power sources and that links free-space optical transmission devices that wirelessly transmit the detection signals that are output by the vehicle detectors. (A*)
Abstract