At least one part of a road surface is covered by a photocatalyst layer containing a photocatalyst such as titanium dioxide, etc. An output shaft is provided for transmitting the steering input from the input shaft to a steered wheel assembly of the vehicle. The optical space switches are of equal dimension, each having the same number of dual ports. The autonomous mobile unit 1 transmits a first ultrasonic wave, and upon receipt of it, the transponder 20 transmits a second ultrasonic wave.