POTENTIAL BENEFITS OF ADAPTIVE SIGNAL CONTROL STRATEGIES

This paper examines the potential benefit of three adaptive traffic signal control strategies. The study used a traffic simulation model of a typical network of downtown signalized arterials to identify conditions where adaptive signals can provide a benefit over non-adaptive (fixed) traffic signal systems and to compare the benefits among strategies and scenarios. The three signal strategies were : 1) isolated signal optimization, determining optimal cycle lengths and phase splits at isolated intersections; 2) a dynamic corridor optimization scheme, optimizing and synchronizing signals along selected corridors; and 3) advanced actuated signals, extending green lights based on real-time traffic counts and queue lengths. The major conclusions are summarized as follows: 1. When traffic follows an expected pattern, a set of fixed signal timing plans developed to optimize the flow of traffic given that pattern performs well. In this scenario, the benefits of adaptive signal strategies were less then 5%. 2. When traffic is heavier than expected or the major direction of traffic flow deviates from predicted levels, adaptive traffic signals that respond by changing signal cycle lengths, phase spits, and offsets can provide significant benefits. In these scenarios, the average trip time through the network was reduced 3 to 15 percent, 3. When traffic is lighter than expected or the major direction of traffic flow deviated from predicted levels, actuated signals provide even greater benefits by responding to traffic in real time. In these scenarios, the average trip time through the network was reduced by 18 to 24 percent.