Recently, automatic systems that control driving speeds and headway distances while following a vehicle have been developed worldwide. Some products, such as adaptive cruise control systems, have already been installed in upper segments of passenger vehicles. Car following is an important operation in safe and comfortable driving on straight and/or curved roads. The number of traffic accidents involving rear-end collisions is the highest over the last decade in Japan (Iwashita et al., 2011). A rear-end collision occurs when the distance between two vehicles decreases due to deceleration of the lead vehicle and/or higher speed of the following vehicle. The automatic vehicle control system maintains a safe headway distance while following a vehicle and controls velocity according to the relative speed of the leading vehicle, in order to avoid a rear-end collision.