A following distance measuring communication system comprising a transmitter and a receiver which are mounted on the front part of a following automotive vehicle, a time measuring unit connected to the transmitter and the receiver provided on the following automobile, and an answering transmitter-receiver unit mounted on the rear part of a preceeding vehicle. A pulse modulated signal is transmitted from the transmitter on the following vehicle, and this signal is received by the answering transmitter-receiver unit on the preceeding vehicle. At the instant that the signal is received, the answering transmitter-receiver unit on the preceeding vehicle generates a reply signal which is in turn received by the receiver on the following vehicle. The time required for this process is measured by the time measuring unit connected to the following vehicle receiver to determine the distance between the following vehicle and the preceeding vehicle.