The World Bank HDM III model : the findings of research conducted by the LCPC[Le modèle HDM-III de la Banque mondiale : Résultats de recherches menées au LCPC]

The World Bank HDM model (Highway Design and Maintenance standards model) makes technical and economic comparisons between different maintenance or improvement strategies by conducting long term simulations of the performance of the roads in a network with reference to the effects of climate, traffic and the works performed. The usual version of this model is HDM-III for PC which came onto the market in 1987. The latest version of HDM is to be distributed by PIARC and is due to replace HDM-III in the near future. HDM-III has been widely used throughout the world, particularly when donor funding is required. This paper discusses four of the conclusions the LCPC has reached from its use of HDM while participating in studies conducted by French consultants and engaging in its own research. The first part assesses the relative importance of the input variables for the selection of optimum strategies. The second part attempts to identify the limits to use the model, which is not very suitable for low traffic levels where user costs make a negligible contribution to the comprehensive economic appraisal. The third section gives a method for calibrating the pavement prediction coefficients which is based on statistical exploitation of network data. The last section shows the effect of this calibration on the model's output and highlights the importance of this difficult process.