A Practical Perspective on the Benefits of Combined Traffic Assignment and Control Method

Combined Traffic Assignment and Control (CTAC) method has been the topic of academic research for the last three decades. Several Solution Algorithms, Model Formulations, and Implementation efforts have been well documented. Although proven in academic research, the use of CTAC based models is rare in engineering practice. Typically, the practice tends to keep Traffic Assignment and Control Optimization processes separate. By doing so, the control-driver interaction in the traffic system is ignored. Previous research emphasizes that CTAC models can capture the control-driver interaction very well, and that the combined modeling framework should be used in practice. The paper presents a practical perspective on benefits of a CTAC model in terms of conveying near-perfect information to the drivers to make route choice with the possibility of improving traffic controls. Four scenarios were tested on an urban area in Salt Lake City, Utah. Scenarios were tested using Static and Dynamic Assignments with Fixed and Vehicle Actuated Controls. The results show that the total-delay reductions and total-travel time improvements were the smallest when only traffic controls were improved in the study area and the highest when the drivers had near-perfect information to make route choice in combination with improvements to traffic controls. Further applications are needed to compare the benefits under other control types and simulation software.