Investigation of Schedules for Traffic Signal Timing Optimization

About the report:

Traffic signal optimization is recognized as one of the most cost-effective ways to improve urban mobility; however, the extent of the benefits realized could significantly depend on how often traffic signal re-optimization occurs. Using a case study from the Northern Virginia Smart Traffic Signal System (NVSTSS), this project sought to determine how often traffic signals need to be re-optimized to provide the greatest benefits. This project developed a new traffic signal timing plan evaluation and optimization program by combining the Integrated SYNCHRO and Platoon Dispersion (ISAPD) model and the OptQuest optimization program. Based on 2001 (base scenario) and 2004 traffic data, five scenarios of re-optimization time intervals (i.e., 2 weeks, 4 weeks, 8 weeks, 16 weeks, and 1 year) were investigated. Study results indicate that (1) determining time intervals for re-optimization in the NVSTSS is feasible; (2) among the various re-optimization time intervals investigated for the Route 50 case study network, the time interval of 1 year was the best for both midday and the PM peak; and (3) the annual net savings from implementing this 1-year re-optimization time interval could be as high as $107,340 and $254,436, respectively, given the assumptions used in the study. The report recommends (1) the annual re-optimization of the Route 50 corridor traffic signal system; (2) the NVSTSS implementation of the combined ISAPS and OptQuest program for measuring "regrets" of not maintaining the optimal timing plan; (3) the adoption by VDOT traffic engineers of the methodology developed in this study, which is based on the combined ISAPD and OptQuest program, for making decisions regarding traffic signal re-optimization; and (4) a future study to investigate the impact of traffic volume growth rates and changes in turning movements as a means of assisting with determinations about traffic signal timing plan re-optimization.

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