In an electric vehicles sharing system, a number of (electric) vehicles are stored in ports and are used by drivers to achieve assigned objects. Herein, multiple vehicles run together in column in an automatic follow-up manner in such a way that following vehicles which are normally unmanned automatically follow up with a manned preceding vehicle. Each vehicle is equipped with ultrasonic sensors, which are arranged in a front portion and a rear portion respectively. Normally, each vehicle detects a travel direction thereof (i.e., a forward or backward direction) to activate only a sensor which matches with the travel direction. Thus, ultrasonic waves radiated from the ultrasonic sensors do not mutually interfere with each other among the vehicles. If a vehicle detects an obstruction being located within a deceleration decision range by the ultrasonic sensor, it is being decelerated while it also transmits a deceleration instruction to other vehicles by radio communication, so that the other vehicles are being decelerated. Thus, it is possible to keep a constant distance between the vehicles which run together in column. If a failure occurs on a sensor of a following vehicle being arranged in the travel direction, the following vehicle transmits failure information to its ahead vehicle which runs ahead of the following vehicle, so that the ahead vehicle automatically activates a sensor which is arranged in a direction reverse to the travel direction. Thus, it is possible to compensate absence of detection due to the failure.