Improved Detection and Control System for Isolated High-Speed Signalized Intersections

High-speed signalized intersections have both safety and efficiency problems. The safety problems traditionally have been overcome by using advance detectors. However, at relatively moderate flow rates, multiple advance detector systems tend to extend the green phase to its maximum allowable duration (i.e., max-out). At max-out, drivers on the intersection approach may be faced with the decision to proceed or stop. This creates the safety problem the system was intended to prevent. Also, extending phases to their maximums increases delays to other movements. A new approach to high-speed intersection control is outlined—a dynamic dilemma zone allocation system that uses measured vehicle speeds with a control algorithm to decide when to end the signal phases. The new system was evaluated by simulation and field installation. In both instances, the new system indicated it could improve safety and maintain efficient operations at high-speed intersections.