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

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.