Transportation in the United States presently uses about 25 percent of the total annual energy budget. Over 95 percent of this energy is supplied by petroleum fuels, and the biggest users are motor vehicles. Differences in modal efficiencies are shown, with motor vehicles and aircraft the least efficient energy users. The growth in energy use by transportation is shown to be about 4 percent per year and due to increasing modal energy intensiveness shifts in traffic from low intensiveness modes to high intensiveness modes, and increasing per capita use of transportation. This growth has been supported by abundant and cheap supplies of petroleum fuels. As these become less plentiful and more expensive, one may expect to see more small cars, shifts from air and highway modes to buses, trains, and pipelines, and changes in personal transportation habits which reduce the demand for transportation itself. 22 pp. Ref.