Adaptive Left Turn Phasing
Allison C. Meadors and Thomas Urbanik II, Texas A&M University, July 1997, 42 pp. (465070-1)
As technology in the traffic controller industry continues to improve, controllers are now more responsive to changing traffic conditions. Taking advantage of the advances in traffic controller technology, the Texas Transportation Institute (TTI) designed an adaptive left turn feature for a signal controller. Automatic Signal / Eagle Signal has introduced this logic internal to their EPAC 300 controller which is capable of deciding and implementing when a separate left turn phase should be provided or when permissive operation is acceptable based on traffic conditions. The adaptive left turn feature was tested for a wide range of left turn volumes and opposing through volumes. Measures of effectiveness that were examined included cycle length, average stopped delay, total delay, and queue length. It was determined that the adaptive feature activated in the controller typically provided a benefit to the opposing through traffic, some disadvantage to the left turning traffic, but generally a benefit to the overall intersection.
Keywords: Left Turn Phasing, Adaptive Signal Control, Traffic Signal Simulation
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Reference Report #465070-1