Quantifying the benefits of adaptive split feature on the operation of coordinated actuated traffic signal system

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Coordinated actuated traffic signal systems have been widely deployed in urban and suburban areas as they provide progression along the major corridors. However, it has been often observed that uncoordinated cross street movements experience higher delay under the coordinated actuated signal systems due to their inability to adjust maximum green times (or force-off points). A few studies mentioned the use of adaptive maximum or split to dynamically adjust maximum green on uncoordinated movements. However, no field implementation results were reported. The purpose of this study was to quantify the impacts of implementing an adaptive split feature on the operation of coordinated actuated traffic signal system through simulation, and then to validate such impacts through a field before-and-after study. The travel time on the coordinated arterials and the stopped delay on key approaches were selected as Measures of Effectiveness (MOEs) to assess the performance of adaptive split feature at the coordinated actuated signalized intersections. The field before-and-after study showed that adaptive split feature resulted in 18 to 38% reduction of stopped delay on cross street uncoordinated movements which is very similar as that estimated by simulation model. In addition, the travel time comparison of before-and-after study also showed that adaptive split feature would not have negative impact on the performance the coordinated approaches.