Development of a Platoon-Priority Control Strategy with/out Smart Advance Warning Flashers for Isolated Intersections with High-Speed Approaches


Henry Liu, Sundeep Bhimireddy

July 2009

Report no. Mn/DOT 2009-23

Most of the rural or suburban high-speed isolated intersections have higher traffic volumes on the major approach compared to the minor approach. The vehicle platoons on major approach are often forced to stop frequently due to conflicting calls placed by few vehicles on the minor approach. To overcome this issue, platoon-priority signal control systems have been developed to progress platoons efficiently at these intersections in a number of previous studies. In addition, Advance Warning Flashers (AWF) are used at these intersections to provide advance warning of end of green to the 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 existing dilemma-zone protection provided by loop detectors and also increases delay on the minor approach. Recently, Advance Warning of End of Green System (AWEGS) has been developed to provide advance warning at these intersections without having to hold green after gap-out. The purpose of this research study is to develop and evaluate the benefits of an integrated system which provides platoon-priority, advance warning of end-of-green, and also dilemma-zone protection at the end-of-green for rural high-speed isolated intersections. Cabinet-in the-loop tests were performed using a real world scenario. These study results showed 50 percent reduction in delay and stops on the major approach with platoons. It was 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 7 to 8 seconds earlier in the majority of the cases.

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