Improving SCATS Operation during Congestion Periods Using Internal/External Traffic Metering Strategy

Traffic metering is one of the effective strategies of preventing gridlock at urban signalized intersections during oversaturated conditions. This strategy could be implemented by adjusting signal timing schemes of the connected intersections of congested network in dynamic setting. This paper demonstrates the benefits of internal/external traffic metering strategy on a real case study in Tehran, the capital of Iran. For this purpose, the model outputs have been considered as input to set of SCATS scenarios for signal timing. In each test case the system is forced to use plans obtained from the model instead of using common built-in plans that had been used before, and the performance is measured using the VISSIM simulator to show differences. The results show significant improvement in network average travel time when using internal/external traffic metering strategy. Additionally, the average queue lengths are maintained near the optimal level since the model utilizes upstream arterial capacity.