The Highway Development and Management Model (HDM-4)1 is a software system for evaluating options for investing in road transport infrastructure. Worldwide, the HDM-4 model is most commonly used as a basis for feasibility studies, in which a road project is evaluated in terms of its economic viability. A more comprehensive type of evaluation based on HDM-4 is a network evaluation, which assesses an entire road network to help decision makers in their strategic planning of road investments and/or the definition of a rational road works program, with or without budget constraints. A network economic evaluation is the most challenging use of the model, but the effort is well justified given the potential savings to be achieved on transport costs by comparing various project alternatives and performing an optimization under budget constraints.
This technical note presents the author’s experience applying HDM-4 and its predecessor, the Highway Design and Maintenance Standards Model (HDM-III), to road network strategic planning evaluations in developing countries, with the objective of providing recommendations and tools to the readers who are involved in strategic planning activities. The purpose of the evaluations, the methodology itself, the input requirements, the challenges, and the presentation of results to decision makers are each reviewed in turn.
The methodology described here attempts to take advantage of all the capabilities of HDM-4, giving due attention to its limitations, and produce usable results. The examples provided represent actual HDM-4 inputs and results obtained from many HDM-4 studies in developing countries in recent years; they were selected from different studies to best illustrate a given evaluation step, but do not otherwise represent a pattern or relationship.