Development of a Platoon Priority Control Strategy Without Smart Advance Warning Flasher for Isolated High-Speed Intersection

Project summary:

A significant number of Mn/DOT signalized intersections operate under isolated control. At many of these signals, it is common for an approaching vehicle platoon to face a red signal because of a single vehicle on one of the conflicting approaches. In addition, Mn/DOT uses advance-warning flashers at selected intersections, which warn motorists on high-speed approaches that the signal phase will be turning yellow. However, the system introduces a trailing overlap of a fixed interval (leading flash) at the end of the arterial phase every cycle, which may cause some dilemma zone problems. This research project was completed in response to the Mn/DOT problem statement on traffic safety and operations requesting the development of an intelligent control system for isolated intersections with high-speed approaches, including platoon-priority control strategy and smart advance warning flashers (AWF). To address the above issues, the researchers aimed to develop an intelligent traffic control system for detecting and moving forward platoons approaching a traffic signal with or without AWF to eliminate the dilemma zone problem and adapt to time-variant traffic conditions. In order to evaluate and improve the proposed control system, hardware-in-the-loop simulation was used and system performance improvements were quantified in terms of operational efficiency and safety. The research team developed an analytical model that can evaluate platoon-priority traffic signal strategy under various conditions and tested the platoon-priority strategy using the hardware-in-the-loop simulation. These study results showed a 50 percent reduction in delay and stops on the major approach with platoons, and found that the total intersection delay and stops were reduced by as much as 20 percent. The system was also successful in providing advance warning to the motorists by predicting gap-outs seven to eight seconds earlier in the majority of the cases.