Nearly 18 per cent of US GNP is spent on transportation, with about one-half of that amount accounted for by cars and related equipment and infrastructure. This is down slightly from its 20 per cent GNP share held over most of the period following the Second World War, a reduction that has been attributed principally to recent economic deregulation of the for-hire industries. Transportation also constitutes a major part of business investments, representing about 13 per cent of total expenditure on new plant and equipment. In addition, transportation is a major consumer of other industries' products, accounting for some 70 per cent of the rubber, 64 per cent of the petroleum, and a quarter of the steel and cement produced (TPA, 1988; see also Deakin and Garrison, 1986). Trends in mileage since 1982 have been mixed. Airways have grown to some 381,084 miles; highways have also increased, more slowly, to 714,255 miles in the federal-aid classifications. Intercity bus routes have been cut back sharply, while urban transit services have been trimmed in some areas but expanded elsewhere for little net change. Petroleum pipeline mileage decreased somewhat, and inland waterway mileages have grown only marginally. The rail system lost another 17,000 miles, bringing its mileage to less than two-thirds of that in 1945 (TPA).
