Link-Journey-Speed Model for Arterial Traffic

Abstract

Real-time traffic information, such as travel time or its inverse—journey speed—is critical to the successful implementation of advanced traveler information systems. Yet it is often costly to measure travel time or journey speed directly. Reliable methods have been developed to estimate travel time and journey speed for freeways. Estimation models for arterial travel time, however, are lacking. A simple model for estimating travel speed over an arterial link is presented. The model combines two speed estimates—one from critical volume to capacity ratio and the other from volume and occupancy measured by loop detectors—to produce more accurate estimated link journey speeds that can be used to provide real-time assessment of traffic congestion levels on arterial streets. A preliminary evaluation of the proposed model is also provided, and the model is compared with two other arterial travel time models. Limitations of the model are explained, and areas for potential improvement are suggested.