Simulation-Based Testbed Development for Analyzing Toll Impacts on Freeway Travel

Traffic congestion has been a worldwide problem in metropolitan areas all over the world. Toll-based traffic management is one of the most applicable solutions against freeway congestion. This research chooses two toll roads, the SR-167 HOT Lane and the SR-520 toll Bridge (i.e. Evergreen Point Bridge), as study sites for simulation testbed developments to evaluate the toll impact on freeway operations. The research approach proposed in this study consists of three steps: first, external modules are developed to enable VISSIM models to simulate various traffic operations with complicated tolling schemes; then, a standardized calibration procedure is proposed for freeway traffic simulation to enhance the models' creditability; and finally, a statistical method is developed to analyze simulation outputs against data autocorrelation problems. Two VISSIM external modules were developed for evaluating toll impacts on freeway operations in this research. For the SR-167 HOT Lane site, an external tolling control module using the Component Object Model (COM) interfaces was developed to dynamically adjust the toll rate based on real time traffic conditions. For the SR-520 Evergreen Point Bridge site, an external routing module using Car2X module is developed to dynamically update vehicle routing. These external modules enabled testing customized tolling strategies often needed in toll impact studies. The simulation results from the SR-167 HOT Lane study site found that among all the three operational strategies, HOT Lane Operation with Dynamic Toll outperforms the other two strategies under various traffic demand conditions. Compared with the HOV Lane Operation, Dynamic Toll strategy makes significant improvement on GP lane performance at regular segments, merging areas, on-ramps, and off-ramps. Compared with the Time-of-day Toll Rate strategy, Dynamic Toll strategy is more flexible under a variety of traffic demands. The simulation results of the SR-520 toll Bridge found that with an increase in toll at SR-520, the travel speed on SR-520 tends to increase and the speed on I-90 tends to decrease as more vehicles are diverted to use the non-tolled alternative. However, the change on I-5 and I-405 after tolling is insignificant since the number of vehicles turning from SR-520 to I-90 is much smaller than the existing volumes on I-5 and I-405. The two simulation testbeds developed in this study were applied to the SR-520 Evergreen Point Bridge and the SR-167 HOT Lane projects and the results were satisfactory. These testbeds are capable of studying various customized tolling strategies on freeway operations. The methodology developed in …