Methodology for Determination of Optimal Traffic Responsive Plan Selection Control Parameters

Closed-loop traffic control systems can be operated by either Time-of-Day (TOD) mode or Traffic Responsive Plan Selection (TRPS) mode. When properly configured, the TRPS mode has the greatest potential to provide an optimal operation due to its ability to accommodate abnormal traffic conditions such as incidents, special events, and holiday traffic. Most importantly, the TRPS mode can reduce the need for frequent redesign/updates to signal timing plans. Although TRPS mode can provide a more optimal and a snappier operation than the TOD mode, numerous parameters (e.g., cycle level parameters, directionality parameters, smoothing factors, weighting factors, etc.) have to be set up correctly for the system to work as intended. Otherwise, TRPS mode may select inappropriate timing plans or cause the closed-loop system to run in a continuous transitioning state. To date, there have not been any formal guidelines for selection of robust and optimal TRPS system parameters and thresholds. Due to the lack of formal and clear comprehensive guidelines, traffic engineers usually revert to the TOD mode of operation for its ease of setup. As a result, the benefits of closed-loop systems are not fully utilized. This report provides a novel methodology for robust and optimal selection of TRPS parameters and thresholds. The report discusses the application of the methodology using data from two closed-loop systems in Texas and demonstrates that the proposed methodology can result in up to 100 percent accurate identification of optimal timing plans. The report also shows potential benefits ranging from an annual savings of $27,630 to $5,042,200 per intersection in delay reduction alone.