Operational impacts of Transit Signal Priority (TSP) in Adaptive Signal Control Technology (ASCT) environment

The study assessed the operational performance of Transit Signal Priority (TSP) in an Adaptive Signal Control Technology (ASCT) environment using PTV Epics/Balance local controllers in a microscopic simulation setting. The analysis was based on a 4-mile study corridor in Florida. Three microscopic simulation VISSIM models, a Base model, a TSP model, and TSP operating in the ASCT environment (ATSP) model were developed. The Base model was calibrated to represent field conditions. The ATSP model provided substantial savings in travel time and average vehicle delay compared to the Base and the conventional TSP model operating in actuated conditions. Under the ATSP scenario, the study corridor experienced up to 13.40% reduction in travel times for buses and all other vehicles, and up to 11.00% reduction in average vehicle delay for buses and all other vehicles. The results were statistically significant at a 95% confidence level. To better quantify the mobility benefits of ATSP, Mobility Enhancement Factors (MEFs) were estimated. MEFs are multiplicative factors used to estimate the expected mobility level of ATSP. A MEF < 1 implies that ATSP yields mobility benefits. The MEFs based on travel time for buses and all other vehicles were estimated to be 0.8780 and 0.9100, respectively. The MEFs based on average vehicle delay for buses and all other vehicles were 0.8960 and 0.9230, respectively. The ATSP model was also found to improve cross-street delay. The study findings may provide transportation agencies with a deeper knowledge of the potential of the Epics/Balance controllers in improving traffic operations.