In this paper we present estimates for the external costs of heavy-duty vehicles. The assessment of environmental impacts through air pollution is based on the ExternE methodology and it is part of a European wide project co-funded by the European Commission. It is based on a detailed 'impact-pathway analysis', which quantifies impacts on human health and the environment in 4 consecutive steps: specification of emissions, dispersion simulation, impact assessment with dose-response functions and monetary valuation. Until now, we have only assessed externalities of Belgian passenger cars with this methodology. This paper is the first in which our results for buses and lorries in Belgium are presented and discussed. Different types of vehicles and technologies are then compared while taking differences in capacity (freight or passengers) into account. Calculations with a simplified world model provide us with a means to distinguish the different impacts that are dominant in cities, rural areas and on highways. An attempt is then made to calculate the total external cost of heavy-duty transport in Belgium. For this goal, detailed data on the composition of the fleet of lorries and buses, yearly mileage and geographical mileage distributions were incorporated in our assessment. Finally we relate these external costs to the fuel consumption of the vehicles in our comparison. Differences in technology (e.g. the size of the diesel engine, emission control) or differences between typical trajectories (e.g, more highway traffic for the largest trucks) lead to different air pollution impacts for the same amount of fuel consumed. The results of this comparison yield important information for discussions on fuel pricing policy. The assessment can be extended to include trains and inland shipping for intermodal comparisons.
