Evaluation of Service Reliability Impacts of Traffic Signal Priority Strategies for Bus Transit

Recent progress in technology has facilitated the design, testing, and deployment of traffic signal priority strategies for transit buses. However, a clear consensus has not emerged about the evaluation of these strategies. Each agency implementing these strategies can have differing goals, and there are often conflicting issues, needs, and concerns among the various stakeholders. To assist in the evaluation of such strategies an evaluation framework and plan was developed that provides a systematic method to assess potential impacts. The use of this framework and plan is illustrated on the Columbia Pike corridor in Arlington, Virginia, with the use of the INTEGRATION simulation package. In building on previous efforts on this corridor, the work presents a method of simulating conditional priority to late buses to investigate the impacts of priority on service reliability. By using the measures developed in this research, a conditional priority strategy designed to increase bus service reliability without resulting in severe traffic-related impacts was tested. Simulation results indicated statistically significant improvements of 3.2% in bus service reliability and 0.9% for bus efficiency, whereas negative traffic-related impacts were found in the form of increased overall delay to the corridor of 1.0% on a vehicle basis or 0.6% on a person basis. These results are also comparable and consistent with the results of other research.