VEHICLE AND DRIVER EFFECTS ON JUNCTION GAP ACCEPTANCE

Abstract

Observations of driver's gap acceptance were made at four non-urban t junctions in Surrey and Sussex. The movements studied, using a video technique and a microprocessor, were a left turn merging with the traffic in the major road, and a right turn crossing the major road to a minor road. Empirical relationships between gap acceptance and the time taken to complete a turn are derived for cars. Turning goods vehicles as a class show significantly longer median accepted gaps than turning cars. Differences between the median accepted gap for different classes of vehicle are explained largely by the manoeuvre time that each class requires. The effect of passengers was studied, but no consistent effects were apparent. Women drivers were found to have longer median accepted gaps than men in all cases. Car drivers who accept short gaps complete their manoeuvres more quickly than those accepting longer gaps. The gap acceptance response appears to be directly related to the acceleration capabilities of vehicles. A conflict simulation model was used to assess the accident risks. This showed that drivers with short manoeuvre times appeared to be involved in more and more severe model conflicts than those with long manoeuvre times. (TRRL)