MULTI-MODAL SIGNAL PROGRESSION DESIGN FOR ARTERIALS WITH HEAVY TURNING FLOWS
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Most urban commuters have long been plagued by congestion in traffic networks and the resulting impacts on safety as well as travel time uncertainties. Since such undesirable traffic conditions in urban arterials are mainly at intersections, traffic researchers often rely on various signal control strategies to smooth traffic flows and minimize excessive delays. Although the advance in communications and control technologies over the past decades has enabled the traffic community to progress significantly on this regard, much, however, remains to be done to achieve the goal of having an efficient and safe traffic environment. Hence, this study has developed an integrated multi-modal signal progression system that allows the traffic engineers to apply different modules of the developed system to produce the best set of signal control plans that can effectively work under various constraints associated with arterial traffic patterns and roadway geometric features. The first primary function of the developed arterial progression system is designed to maximize the progression efficiency of passenger cars on a long arterial comprising heavy left-turn volumes, limited turning bay length, and near-saturated intersections. The developed system with such an embedded function can produce concurrent progression for both the through and left-turn movements with the least likelihood of incurring mutual blockage between them and uneven traffic queues among all critical locations on the arterial. To decompose a long arterial into the optimal number of control segments with well-connected and maximized progression bands, this study has further offered a function of a two-stage optimization process to tackle various critical issues that may prevent vehicles from progressing smoothly over the entire long arterial. To accommodate heavy passenger car and bus flows over an urban arterial and ensure the progression quality for both modes, this study has advanced the system with an innovative function that can offer concurrent progression to the best selected mode(s) and direction(s), based on traffic volume, bus ratio, and geometric conditions. By weighting the progression bandwidth with the passenger volumes and taking into account all critical issues that may result in their mutual impedance, such an embedded function of the developed arterial control system can achieve the objective of maximizing the benefit for all roadway users and for all modes. Most importantly, to ensure the effectiveness of the developed system’s key functions under various arterial traffic patterns and control objectives, this study has integrated all key modules developed for, such as, the arterial signal design, allowing users to contend with most challenging scenarios, concurrently decomposing a long arterial into the optimal number of control segments for both modes, maximizing their progression bands within their respective segments, circumventing all geometric constraints, and balancing the progression length and bandwidth between the competing modes. In view of computing efficiency associated with the execution of all interrelated optimizing functions, this study has also designed a customized algorithm to minimize all computation-related tasks. Rigorous evaluation with extensive numerical studies has verified the effectiveness of the developed arterial system’s key functions, and evidenced their contributions with respect to offering best progression and minimizing traffic delays. The developed system’s flexibility in circumventing various roadway constraints and traffic queue spillback has also been confirmed from the results of comprehensive simulation experiments with different critical traffic scenarios.