Building Our Way Out of Congestion? Highway Capacity for Twin Cities

What would it take to build our way out of congestion in the Twin Cities? As part of this research project, researchers identified a method to answer that question and found a minimal set of highway capacity expansions that would accommodate future travel demand and guarantee mobility. The problem of identifying a set of capacity expansions that are in some sense optimal, while accounting for traveler reaction, is known as a network design problem. A literature review reveals numerous formulations and solution algorithms over the last three decades, but the problem of implementing these for large-scale networks has remained a challenge. This project presents a solution procedure that incorporates the capacity expansion as a modified step in the Method Successive Averages, providing an efficient algorithm capable of solving realistic problems of real-world complexity. Application of this method addresses the network design problem for the freeway system of the Twin Cities by providing a lower bound on the extent to which physical expansion of highway capacity can be used to accommodate future growth. The solution estimates that adding 1,844 lane-kilometers, or 1,146 lane-miles, would be needed to accommodate the demand predicted for the year 2020.