Network Design Programming of U.S. Highway Improvements

This paper describes a network design approach to the selection and programming of alternative route improvements to the U.S. highway network of interstates, four-lane urban highways, and principal rural arterials. Alternative route-improvement strategies are defined as mutually exclusive sets of link improvements that can be programmed for construction within any decade of a multidecade planning horizon. The two improvement strategies considered for each route are: (1) To make every link median divided with controlled access and at least four lanes; or (2) to make every link at least four lanes, but without any changes to median division of access control. The examples of this paper evaluate 536 potential improvements to 289 major highway routes between adjacent Bureau of Economic Analysis (BEA) regions, or nearly two improvement strategies per route. Route-improvement strategies programmed for each decade are constrained by 10-year funding allocations. A trip distribution model is used to distribute commodity shipments forecast for each decade among regions. Route-improvement benefits are computed as changes in the value of the objective function, which is the total discounted interregional shipment cost for all years of the planning period. Since different routes and interregional shipments can share common links, a rank-add-and-swap heuristic solution procedure was developed and applied that accounts for the interdependent costs and benefits of route improvements. Implications of this network design approach for planning future expansions and improvements of the interstate highway network are discussed.