NETWORK PERFORMANCE UNDER SYSTEM OPTIMAL AND USER EQUILIBRIUM DYNAMIC ASSIGNMENTS: IMPLICATIONS FOR ADVANCED TRAVELER INFORMATION SYSTEMS

Abstract

A comparative assessment was undertaken of network cost and performance under time-dependent system optimal (SO) and user equilibrium (UE) assignment patterns, with particular reference to the effectiveness of advanced traveler information systems (ATIS). Both SO and UE solutions were found using a new simulation-based algorithm for the time-dependent assignment problem. Experiments were conducted using a test network with signal-controlled junctions under progressively increasing network loading intensities. A diagnosis of system performance for various intensities of loading was effected using network-level traffic descriptors for both SO and UE assignments. The results affirm the validity of a meaningful demarcation between SO and UE assignments in urban traffic networks and provide useful insights for macroscopic network-level relations among traffic descriptors. These results suggest that ATIS information supply strategies based on SO route guidance could considerably outperform descriptive noncooperative information strategies, especially at moderate to high congestion levels in the network. The results also illustrate the time-dependent nature of the gains achieved by an SO assignment vis-a-vis a UE assignment in a congested traffic network.