The question addressed in this paper asks how to measure the value of additional expenditures for transportation compared to the value of spending for education, health, recreation, or other social services. The relevance of the inquiry has been increased by the rising costs of transportation, by the further pressures on cost from such factors as energy and metropolitan growth, and by the mounting competition for scarce resources in a period of economic uncertainty and expanding consumer demands. The approach suggested for dealing with this practical but elusive question is based on statistical relationships between the movement of people and goods and levels of economic activity in this country and abroad. Both the history of transportation and present day comparisons among nations in different stages of development make it clear that transportation is an essential ingredient of economic progress: the rich enjoy a high degree of mobility and the poor suffer from lack of mobility. At the same time transportation is only the means by which societies achieve other objectives, and there is a limit to the resources that can be effectively allocated to movement rather than to other needs. Going beyond that limit means that the basic objectives of a society will be neglected.