Optimized Policies for Adaptive Control Strategy in Real-Time Traffic Adaptive Control Systems: Implementation and Field Testing

The real-time traffic adaptive control system (RT-TRACS) represents a new, state-of-the-art system in advanced traffic signal control. It was developed cooperatively by a team of U.S. academic, private, and public researchers under the guidance of FHWA. The system provides a framework to run multiple traffic control algorithms, existing ones as well as new adaptive algorithms, as they become available. The optimized policies for adaptive control (OPAC) strategy, which provides a dual capability of individual intersection control as well as coordinated control of intersections in a network, was the first adaptive algorithm implemented within the RT-TRACS framework. The operational features of the OPAC prototype version that was developed for RT-TRACS are presented, and its implementation in the Reston Parkway field research test bed in Northern Virginia is described. The implementation provided valuable insights into the performance of coordinated OPAC under various traffic conditions and site geometry. Observations indicate that the strategy was instrumental in reducing delays and stops, compared with a well-tuned fixed time system that was in place, while maintaining progression along the arterial. Valuable lessons were learned that should lead to improvements in future implementations of adaptive algorithms.