Abstract:We have classified and estimated the social cost of motor vehicle use in the United States on the basis of 1990-91 data. The analysis provides a conceptual framework for viewing social costs, develops analytical methods and data sources, and presents some detailed estimates of some of the costs. The data, methods, functions, and estimates of this analysis can help analysts and policymakers evaluate the costs of transportation projects, establish efficient prices for transportation services, and prioritize research and funding. This analysis cannot, however, tell us precisely what we should do to improve our transportation system. Not only are many of the estimates too generic and uncertain, but, more important, society cares at least as much about equity, opportunity, and justice as it does about economic efficiency. At the end of the day, a total social-cost analysis contributes only modestly to but one of several societal objectives for transportation.