Reducing Time-of-Day Traffic Signal Controller Transitions through Collective Offset Adjustments

Time-of-day transitions are a critical process traffic signal controllers use to ensure coordination when switching between timing plans. There are multiple factors that can influence the time it takes to go through transition. This paper investigates the optimization of traffic signal transitions. The goal is to identify an optimal collective offset adjustment that will be able to reduce the total transition times across coordinated intersections. A mathematical framework was demonstrated to estimate transition times, which was then validated through simulations using the virtual traffic signal controllers. The numerical results from this paper identified an optimal collective adjustment to existing offsets at four coordinated intersections in Tuscaloosa, AL—Hillcrest, Patriot, Bobby Miller, and Mae Hinton. This set of offset was implemented over a 3-day period, and the resulting transition times were compared to a prior baseline, leading to a total transition time reduction from 1,039 to 371 s—a 64.3% reduction as confirmed using automated traffic signal performance measure data. Statistical analysis using Welch’s t-test confirmed the significance of this reduction, with a p-value of 0.0002. The study also highlights the adaptability of the proposed methodology, which can be applied to a wide range of traffic signal controllers while maintaining any relative offsets between coordinated intersections that have been designed by an engineer. These findings contribute to improving traffic flow and reducing delays during transitions, offering a practical solution for traffic management systems.