Relevance of HDM3 Road User Cost Model to Canadian Heavy Vehicles

Operating expenses of the Canadian heavy vehicle fleet exceed several times the expenditures on the public road system, but sound aids recognizing the importance of user costs in road investment decisions are lacking. A state-of-the-art model of user costs, HDM3, is evaluated for relevance to the Canadian heavy vehicle operating conditions, and results of preliminary calibrations for six typical vehicles are presented. The HD M3 model is highly relevant to studying road infrastructure issues. It is also easy to operate and to calibrate, but the cost-roughness slope and the effect of road texture a roadworks decision variable in Canada remain to be validated. The model will become more useful once the effects of congested traffic conditions on operating speeds are incorporated into a forthcoming version. The cost components in need of closer examination are maintenance and depreciation, which are inter-related and further complicated by the manufacturer's practice to include factory warranty costs into the purchase price. Maintenance cost formulas themselves need re-evaluation because they were developed for a low labour-cost environment. The HD M3 relationships for calculating truck utilization should be revised. If the present "adjusted utilization method" is retained, it should be modified to account for the fact that time savings on a haul do not necessarily translate into additional trips, unless tractors are run 24 hours a day and loading/unloading is not a time constraint. Relationships for cargo delay and damage due to road conditions need improvement because these costs are relatively more important in developed countries than in developing ones, for which HDM was originally conceived.