Studies show that the risk of becoming involved in an accident increases when the deviation from the average speed increases. Different layout features such as gentle slopes or an extra climbing lane for lorries are used. In order to provide information for the design end evaluation of lorry drivers' speed behaviour at grades a simple computer program has been developed. It calculates the velocity a vehicle is able to reach at any vertical alignment. In the Dutch road design practice this program is useful in the evaluation of the deceleration on gradients adjacent to tunnels under inland waterways and in calculating the speed of heavy vehicles' acceleration at freeway ramps. The paper also presents the work carried out when selecting the typical lorry. The power to mass ratio is 6.4 kW/ton, which is more than ratios found in most of the current guidelines for road design.
Abstract