IMPLEMENTATION OF COMBINED TRAFFIC ASSIGNMENT AND CONTROL FRAMEWORK BASED REGIONAL MODEL FOR THE WASATCH FRONT REGION

The regional travel demand models are generally macroscopic in nature and do not include traffic controls in the traffic assignment process. In travel demand models, the road capacities are kept fixed within the functional classification of roadways and free-flow-speeds are adjusted to accommodate the impacts of traffic controls and traffic operations. Part of the reason this approach is adopted in travel demand models is there macroscopic application, where the focus is extensively on the region wide results for transportation planning. While there are advantages in using this approach, the cost is usually paid in “lost capacity on projects” due to the absence of traffic operations in modeling; more precisely the absence of traffic controls tend to present partially skewed output from the travel models. Combined Traffic Assignment and Control models can address this issue by including the impacts of traffic controls in the modeling process. This paper evaluates the benefits of combined traffic assignment and control modeling framework implemented on a regional scale compared to a traditional four step regional travel demand model. The study quantifies the benefits in terms of providing network travel time information to drivers to make route choice in comparison to improving the traffic controls on a large regional network (on a mesoscopic level). Several experiments were performed on a study area using Static Traffic Assignment (STA) and Dynamic Traffic Assignment (DTA) with fixed and vehicle-actuated controls. The study area network is a regional transportation network for the Wasatch Front Region in Utah. The results suggest that if implemented on regional travel models, the CTAC framework can help reduce the VMT and reduce regional delays by over 6%. Further studies are needed to expand on this idea with multimodal modeling and testing on other regional networks.

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