In-tunnel transmission characteristics of VICS radio beacon

The Radio Beacon System provides digital radio transmissions as part of the Vehicle Information and Communication System (VICS). Operating in the quasi-microwave (2.5 GHz) band at transmission speeds of 64 kbps, the system enables moving vehicles to be provided with roadway-traffic and location information. According to available reports on tests of this system, a service area of 70 m or more can be secured along open roadways where road station antennas are installed. Since the Metropolitan Expressway Public Corporation plans to construct a number of tunnels in the future, any practical Radio Beacon System will require that road stations also be located in tunnels. To confirm the possibility of communication in tunnels, the authors conducted an in-tunnel-evaluation test of the system to clarify in-tunnel transmission characteristics, which seem likely to be quite different from those on open roadways