Bandwidth-Constrained Delay Optimization for Signal Systems

T efficient operation of traffic signal systems with complex phasing has been a constant challenge for the traffic engineer, In recent years, the accelerated and continued growth in traffic demand has produced congestion and a cfecreased Icvel of service unprecedented on many urban and suburban facilities of the country. It is apparent that an optimal traffic control plan must be designed and implemented if maximum utilization of the existing facilities is to be obtained. This is particularly critical in view of the growing limitations in resources and funding levels available for new or expanded facilities. Over the past decade, a number of computerized techniques have been developed for optimizing signal timing plans for urban signal systems. These techniques vary in their criteria employed to reach a desired timing plan. Most use the criterion of’either minimizing system delay and stops or maximizing arterial progression bandwidths. Techniques also vary in terms of the traffic v~riablcs considered in the optimization process. However, of the four variables available to the traffic engineer that can be adjusted to provide signal timing plans (i. e., green phase time, offset, cycle length, and left-turn phase sequence), no single existing tcchniquc can include all of them simultaneously in the optimization formulation. The purpose of this article is to report on an approach that integrates the best features of’ the delay/stops optimization and progression bandwidth optimization techniques. Through the integrated approach, all four variables can be explicitly optimized in stages.