Effects of the number of exit lanes on the driving performance of drivers who diverge from highway

Deceleration lanes are designed to improve traffic operation, reduce vehicular interferences, improve safety, and provide an effective transition from high-speed lanes to low-speed ramps. Nevertheless, several studies have shown high crash rates on these road geometries. Moreover, there are no guidelines that could provide designers with clear and updated criteria for appropriately designing deceleration lanes, whilst taking into account the driver’s behavior and the effects of different design variables on driving performance. The main objective of this study is to investigate the driving performance of drivers exiting from the highway under various geometric deceleration lanes conditions. Specifically, the effects of different deceleration lanes on the speeds, trajectories, and decelerations of diverging drivers were investigated, in order to increase the knowledge of driver behavior whilst approaching a highway exit, during the lane-change maneuver, and along the deceleration lane. Thirty one drivers took part in the experiments. Two different tapered deceleration lanes (with a single-lane exit ramp and with two-lane exit ramp, respectively) were implemented using a driving simulator in order to observe how exiting drivers performed, by analysing their speeds, decelerations and trajectories while they were approaching the deceleration lane and were decelerating till the exit ramp. The effects of the number of the exit lanes on the driving performances were then statistically analysed. The main results demonstrated that, for the geometric and operating conditions investigated in this study, a single-lane exit ramp resulted in a poorer performance from the exiting drivers with regard to the operating and safe driving conditions. In fact, it was found that, when a single-lane exit ramp was available, drivers adopted lower exiting speeds and higher decelerations than those using two-lane exit ramp. Therefore, the latter seemed to provide improved performance, by limiting the interferences of the diverging drivers with through traffic, with regard to speed differentials and deceleration maneuvers along the through lanes.