Intelligent transportation systems (ITS) encompass a broad range of wireless and wire line communications-based information and electronics technologies. When integrated into the transportation system's infrastructure, and in vehicles themselves, these technologies relieve congestion, reduce emission, improve safety and enhance productivity. ITS is an emerging global phenomenon benefiting the public and private sectors alike. For example, ITS makes it possible to implement a number of government regulations and processes more economically, and to improve corporate productivity through time savings, reduced operating costs and energy consumption, and enhanced reliability and safety. The field of intelligent vehicles is rapidly growing worldwide. Intelligent vehicles offer the potential to significantly enhance safety and operational efficiency. As one component of ITS, intelligent vehicles use sensing and intelligent algorithms to understand the vehicle's immediate environment, either assisting the driver or fully controlling the vehicle. Intelligent vehicles function at the control layer to enable the driver vehicle subsystem to operate more effectively.