Evaluation of Integrated Platoon-Priority and Advance Warning Flasher System at High-Speed Intersections

Most rural or suburban high-speed isolated intersections have higher traffic volumes on the major approach compared with the minor approach. Often these intersections are not close enough to one another to provide coordination and are not far enough apart to disperse vehicle platoons completely on the major approach. These major-approach vehicle platoons are forced to stop frequently because of conflicting calls placed by a few vehicles on the minor approach. As a result, these intersections operate poorly, especially during peak periods. In addition, advance warning flashers are used at these intersections to warn motorists of the end of the green. The conventional method uses the trailing overlap green, which holds the green for a fixed time after gap-out. This trailing overlap green replaces the existing dilemma-zone protection provided by loop detectors and also increases delay on the minor approach. Recently, platoon-priority signal control systems have been developed to progress platoons efficiently at these intersections. In addition, the Texas Transportation Institute has developed the advance warning end-of-green system to provide advance warning at these intersections without the necessity of holding the green after gap-out. In this study, these systems are integrated and the performance of the system is evaluated in terms of delay, stops, and advance warning time. Cabinet-in-the-loop tests performed with a real scenario suggested potential benefits of 50% reduction in delay and stops on the major approach experiencing platoons. It was also found that the total intersection delay and stops were reduced by as much as 20%.