Since approximately 70% of Japan's national land is occupied by mountainous areas, such areas almost necessarily appear when traffic networks between large cities are developed. Hence, if traffic networks are developed such that they thread through mountainous areas, costs can be reduced. However, the roads will wind making it an acident-prone area. However, even if the road is made straight by constructing a tunnel, new risks will occur because inside of the tunnel is a dark closed space.
Thus, one of the devices for reducing such new risks as much as possible is the radio re-broadcasting system.
By installing the radio re-broadcasting system, radio broadcast can be listened to even inside the tunnels, which could not be previously be heard. In addition, in emergency cases, this system can provide information directly to the drivers who are driving inside tunnels by interrupting the radio broadcast and providing interruptive broadcast (providing information).
This is a system by which drivers can receive information without using any special devices or conducting any needless operations, simply by listening to the radio during driving.