Grand Challenges in Modeling and Simulating Urban Transportation Systems

Congestion in surface transportation systems has reached unprecedented levels, and now costs tens of billions of dollars each year in productivity and extra fuel costs in the U.S. alone. Accidents kill tens of thousands of individuals each year, and pollution from vehicle emissions degrades the quality of life of every citizen. Given the cost and danger of experimenting with operational systems and limitations of purely analytic techniques, effective modeling and simulation (M&S) tools are essential to solving these problems. However, existing simulation tools are far from adequate, and typically focus on only a particular aspect of the problem. This paper surveys the use of M&S in modeling surface transportation systems. A grand challenge is proposed to realize robust, accurate models of transportation infrastructures and its users for large metropolitan areas over time scales ranging from minutes to years. M&S tools are needed to predict the impact of both planned and unplanned changes as well as the introduction of new technologies, to prioritize infrastructure investments, to manage the system under unexpected operating conditions and traffic loads, to develop emergency and securityrelated contingency plans, and to test the impacts of various governmental policies on regional economic viability. Meeting this challenge will require a holistic approach that includes accurate models of individual travelers and businesses, as well as the transportation infrastructure itself.