Route Level Evaluation of Queue Lengths Display at the Amsterdam Orbital Motorway

Abstract

Report published by the Delft University of Technology, Transportation Planning and Traffic Engineering Section, commissioned by the Ministry of Transportation, North Holland Directorate. The use of Variabie Message Signs (VMS's) is generally considered to be a powerful tool to influence (en-route) route choice in order to improve safety and comfort while driving, to improve the network performance, and optimally make use of the available capacity. Assessing whether such effects actually occur when VMS's are installed is a difficult task. This report presents the results of an extensive evaluation study carried out at installing 14 new VMS's at the Amsterdam orbital motorway. The study involves a number of issues. First, the relation between the messages displayed at the VMS and the travel times experienced by drivers is analyzed. Second, a stimulus response analysis is used to find out how drivers respond in reality to the messages is described. Finally, a network-wide analysis of aggregate performance indicators, like queue length, distance traveled, and time spent on the network is included. The study showed that the use of VMS's has a positive impact on network performance in the Amsterdam freeway system. Total congestion has slightly decreased, while traffic performance has slightly increased. Variation in congestion has decreased, as weil as variation in average travelspeed. This implies that travel time has become more reliable and that the traffic flow is more homogeneous. The technical assessment showed that the displayed queue lengths, if interpreted correctly by the drivers, are a good measure for the expected delay. User response analysis, measured by modeling route choice as a function of information provided, showed that information has a significant effect on route choice. In general, the VMS's were found to be a tooi to improve the efficiency and reliability of the system.