  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.
