Selecting and scheduling an optimal subset of road network upgrades

We consider the problem of choosing a subset of proposed road network upgrades to implement within a fixed budget in order to optimize the benefit in terms of vehicle hours travelled (VHT), and show how to render the solution of this problem more tractable by reducing the number of traffic assignment problems that must be solved. This technique is extended to develop a heuristic algorithm for finding a schedule of road upgrades over a planning period that maximizes the bet present value of the resulting VHT reductions.