Abstract:In our analysis of the social cost of motor-vehicle use, many of our date sources, methods, and estimates of cost apply in the first instance to all classes of motor vehicles. For example, we are given, or can estimate from primary data, the following:

• total government expenditures on the highways
• the air-pollution damage cost of emissions from gasoline service stations
• the air-pollution damage cost of emissions of PM10 from reentrained road dust
• highway-patrol expenditures
• the cost of garages and parking spaces
• the cost of oil spills, per barrel of oil

All of these costs pertain to all motor vehicles: all autos, trucks, and buses. Although it can be interesting to estimate the cost of all motor-vehicle use, it typically will be more useful to estimate the cost of different classes of vehicles or of different fuel types, because analysts, policy makers, and regulators typically are interested in specific classes of vehicles, and specific fuels, rather than all motor-vehicles as a group. (For example, pollution regulations are set for individual classes of vehicles, not for all motor vehicles as a class.) Thus, it is useful to carry the analysis of total social cost a step further, and take a cost that initially applies to all motor-vehicles and apportion it to specific vehicle and fuel classes. This report develops such "allocation factors," which can be used to apportion or disaggregate a total cost to specific vehicle and fuel classes.