INTER-VEHICLE DISTANCE MEASUREMENT APPARATUS

An inter-vehicle distance to a preceding or following vehicle is reliably determined by using a simple processing, to alert the following vehicle to approach a dangerous range. The distance measurement apparatus includes a pair of light-receiving devices disposed on image-forming surfaces of lenses and having sensor lines and measurement windows on each sensor line at a certain interval, a distance detection device, a white line detection device and a vehicle detection device. The distance detection device detects distances at points, the coordinates of which are specified by the sensor line numbers and measurement window addresses. By using the detection results, the white line detection device detects a sensor line in which a white line on a road surface is present. By using the detection results obtained from the distance detection device relating to the sensor lines in which the white line is not present, the vehicle detection device checks a presence of a vehicle and outputs information on the inter-vehicle distance and the direction of the vehicle. The following vehicle may be alerted by flashing the brake lights.