Transportation engineers and planners worldwide are faced with the challenge of improving transit services in urban areas using low cost means. Transit signal priority is considered to be an effective way to improve transit service reliability and efficiency. In light of the interest in testing and deploying transit signal priority on a major arterial in Northern Virginia, this research focuses on the impacts of transit signal priority in the U.S.1 corridor in Fairfax County in terms of benefits to transit and impacts on other traffic. Using a simulation tool, VISSIM, these impacts were assessed considering a ten second green extension priority strategy. The results of the simulation analysis indicated that the Fairfax Connector buses benefit from the green extension strategy with little to no impact on the other non-transit traffic. Overall, improvements of 3.61% were found for bus service reliability and 2.64% for bus efficiency, while negative impacts were found in the form of increases in queue lengths on side streets by a maximum value of approximately one vehicle. Because this research has provided a foundation for the evaluation of transit signal priority for VDOT and Fairfax County engineers and planners, future research can build upon this effort. Areas identified for future research include the provision of priority for the entire bus route; combination of emergency preemption and transit priority strategies; evaluation of other priority strategies using system- wide priority concepts; and the impacts of priority strategies in monetary terms. / Master of Science

Heavy traffic volumes in peak hours accompanied by closely located signalized intersections and nearside bus stops on U.S. 1, result in congestion and traffic delays that bus transit may be able to alleviate to some extent. The capital investment and operating costs of other transit solutions such as "Bus Rapid Transit" and "Heavy Rail Transit" projects were found to be cost prohibitive compared to bus transit signal priority (TSP) options. Successful implementation of a limited TSP pilot project led local authorities to conclude that TSP should be extended to the full length of the Fairfax Connector bus routes on U.S. 1. This research focused on testing the impacts of a ten second green extension priority strategy for all the northbound transit buses in the morning peak period at twenty-six signalized intersections along U.S. 1. A micro simulation model VISSIM 3.7 was used to analyze the impacts of TSP. The simulation analysis indicates that the Fairfax Connector buses might benefit from the green extension strategy. Overall, improvements of up to 4% for transit travel time savings and 5-13% reduction in control delay for transit vehicles were observed. Considering all side street traffic, the total increase in maximum queue length might be up to 1.23%. Future research possibilities proposed include the evaluation of different priority strategies such as an early green, red truncation and queue jumps. Impacts of using a dedicated lane for transit buses along with TSP can also be evaluated. Conditional transit signal priority may also include bus occupancy levels and bus latenesses. / Master of Science