Accident sometimes occur, particularly on high-speed roads because the driver of a following vehicle cannot stop in an emergency without overtaking the rear of the vehicle ahead. If he cannot avoid this vehicle he must collide with it, and even if he avoids it he may have an accident through going out of control or colliding with another vehicle. Accidents of this kind are called close-following accident. Accident data are examined to try to form an estimate of the frequency of such accidents on motorways. The vehicle ahead may stop very suddenly if involved in a collision, but such extremely sudden stops are not the only danger. Because braking capacity varies from vehicle to vehicle there may be danger even if the vehicle ahead is braked hard. The chance that the following vehicle cannot stop in time if the vehicle ahead is braked as hard as possible may be estimated from the distribution of braking capacities among vehicles. The variation of this probability with following distance, speed, and reaction time is evaluated and the effect is considered.
Abstract