Abstract
Conventional traffic-control strategies have limitations in handling unanticipated traffic demands. An adaptive traffic-signal control is expected to mitigate this problem and improve overall system performance. Furthermore, with the increasing needs of evolving intelligent transportation systems, traffic signals are expected to provide significantly greater functionalities, which can be achieved only by adaptive control. A product of many years of development, Optimized Policies for Adaptive Control (OPAC) represents a significant step forward in adaptive signal-control research. The OPAC strategy was field-tested at a New Jersey site. The performance of OPAC was compared against a well-designed time-of-day signal control. The evaluation was performed under various traffic-demand conditions and included both isolated intersections and arterial sections. The analysis indicated a highly significant improvement with OPAC control. OPAC showed its best performance during oversaturated conditions. It reduced the travel time and number of stops by about 26 percent and 55 percent, respectively, for the entire arterial section. OPAC also improved traffic performance during changing demand conditions. It significantly improved the performance of an isolated intersection during undersaturated traffic conditions. OPAC reduced stopped delay on the major-street approach by 40 percent without affecting the minor-street performance.
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