Planning Applications of Statewide Travel. Demand Models In general, statewide travel demand models differ from MPO models in their wider spatial coverages and emphasis on freight transportation activities (NASEM, 2017). Travel activities between MPO boundaries and/or across state boundaries are not typically captured in MPO models. Statewide models are designed to specifically address these long-distance trips. For example, some routes not covered within MPO boundaries may carry significant amount of traffic that are vital to a state’s economic development. With statewide models, the state departments of transportation (DOT) can evaluate investment proposals involving these routes. Forecasting freight traffic is a major function in some statewide models for environmental impact assessment of statewide transportation plans because the amount of emissions from all the trucks on a state’s highways can be very significant. Many statewide models include separate freight travel models to capture flows of freight trucks on state highways. Freights moving by rail, water, and air are also explicitly modeled with freight mode choice models in some statewide modeling applications. Statewide travel demand models have been used for evaluations involving the following general categories of scenarios (NASEM, 2017): • Infrastructure scenarios • Policy scenarios • Global scenarios Statewide travel demand models are most often used to evaluate different infrastructural investment scenarios, such as new highways or transit lines, extension or improvement of existing facilities, and/or the development of major trip generators (e.g., housing or commercial projects) in specific locations that are expected to influence travel activities beyond spatial boundaries covered by MPO models. Such decisions may also involve abandoning existing facilities. Policy scenarios refers to proposed policy measures intended to reduce travel demand and/or congestion, such as imposing tolls on a highway, designating truck routes, or increasing transit service. Policy scenarios may also involve other regulations actively implemented by a government that do not change the built environment. Global scenarios refer to uncertain future developments, such as economic downturn, population and employment growth, energy price fluctuation, or widespread adoption of autonomous vehicles. Statewide travel models can be used to evaluate how these scenarios can impact a state’s transportation systems, such as testing the range of gas price increase t...
