Optimization Models for Transportation Project Programming Process

Five optimization models are constructed for selecting an optimal subset of projects submitted for a statewide programming process. Our approach develops models that are consistent with user needs and appropriate for the assumptions used in the project prioritization process. Each of the models builds on a basic linear-programming formulation in which a maximization of benefits and minimization of costs is desired. The five models include the following: a priority index that provides a ranking of projects but does not directly facilitate trade-offs between project costs and the ranks (model 1); a model that incorporates a formal approach to making trade-offs between rank and cost (model 2); a model that explicitly includes policy objectives by setting a fixed goal for each objective (model 3); a model that includes a strict budget constraint in addition to requiring that funded projects equal or exceed a fixed goal for each policy objective (model 4); and finally, a model that combines the relative rankings and budgetary constraint (model 5). Models 2-5 are developed in both a continuous and integer variable format, thus generating nine optimization approaches. Models 4 and 5 also introduce a method for determining the improvement in the overall transportation-system performance, given the current budget and decision-maker objectives.