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Center for Transportation Studies


Evaluation of Platoon-Priority and Advanced-Warning Flasher Systems at High-Speed Signalized Intersections

Part of the Advanced Transportation Technologies Seminar Series — 2008 . For more information, contact Shawn Haag at the ITS Institute, 612-625-5608 or

September 9

Henry Liu
Assistant Professor, Department of Civil Engineering

Download Presentation (2.57 MB PDF)

The majority of rural and suburban high-speed isolated intersections are characterized by higher traffic volumes on the major approach than on the minor approach. Often, these intersections are not close enough to one another to support signal coordination, and not far enough apart to allow for complete dispersion of vehicle platoons on the major approach. Vehicle platoons on major approaches are forced to stop frequently due to conflicting signal demands from a small number of vehicles on the minor approaches. As a result, these intersections operate poorly, especially during peak travel periods.

An additional factor affecting performance at these intersections is the deployment of advanced-warning flashers to provide advance notification of the end of green signals to motorists. The conventional method uses trailing overlap green, which holds the green for a fixed time after gap-out. This trailing overlap green replaces the 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. Additionally, Texas Transportation Institute has developed the advance warning of end-of-green system (AWEGS) to provide advance warning at these intersections without having to hold green after gap-out. This presentation describes the integration of these systems, and evaluates their combined performance in terms of delay, stops, and advance warning time. Cabinet-in-loop tests performed using a real scenario suggested potential benefits including a 50 percent reduction in delay and stops on the major approach with platoons;  total intersection delay and stops were also reduced by as much as 20 percent.