Joint Travel Demand and Environmental Model to Incorporate Emission Pricing for Large Transportation Networks

Emission reduction strategies are gaining greater attention as a support of the national objective for a sustainable and green transportation system. A large percentage of the emission contribution that arises from transportation modes are primarily from auto and truck travel. Reductions in highway travel require prudent planning strategies and modeling user response to planner's policies. Modeling planning goals and user response is a challenging task. In this paper a joint travel demand and environmental model incorporates vehicle emission pricing (VEP) as a strategy for emission reduction. First, the travel demand model determines the destination, mode, and route choice of the users in response to the VEP strategy set by the planner. Second, the emission model provides oxides of nitrogen, volatile organic compounds, and carbon dioxide estimates at a very detailed level. A base case and three models incorporate VEP in a multimodal transportation network. The objective function of the base case is the minimization of total system travel time, and the models are designed with the objective of minimizing total system emissions. The user equilibrium method is used for travel to model user responses and is solved by the Frank–Wolfe algorithm. The base case represents do-nothing conditions, and the three models address the interactions between planner's perspectives and user responses to VEP strategies. The proposed model is applied to the multimodal transportation network of Montgomery County (located in the Washington, D.C.–Baltimore, Maryland, region). The case study results show that VEP can be used as a tool for emission reduction in transportation planning and policy.