Abstract: The invention discloses a method and device which allows one to measure distances from one object to a remote object, e.g., the distance from a driver of one car to a car ahead of him. The method allows an observer to determine easily and at any time the exact distance between himself and the object, e.g., a driver can tell, by reading off his speed from the speedometer, whether he is maintaining the necessary safety distance between his car and the car ahead of him, thus enabling him to correct his speed if necessary. The device used for controlling the safety distance comprises a vertically adjustable scaled transparent plate which is mounted adjacent to the windshield of the car in the driver's field of view. The scale markings on this plate consist of a reference line and a sequence of scale lines parallel to the reference line and below it.