Americans travel billions of miles each year, and for every mile they ride, they use energy. Transportation—cars planes, buses, trains, boats—uses up almost half of all the energy consumed by households (see Table 3-1, above). In terms of thousands of miles traveled, the car is the biggest energy user, accounting for almost 90 percent of all intercity passenger miles of travel (Table 4-1). In terms of the amount of energy used per passenger mile, the airplane uses the most energy with the car second (Table 4-2).

Americans traveled an average of 6,000 miles per person between cities in 1971, and undoubtedly more miles per person since then, for the figure goes up every year. But average figures can be misleading; they imply an equality that does not exist. Some people travel a great deal; some not at all. Some stay at home by choice, others because they cannot afford to leave even for a short trip. A very important influence on personal travel is income. If a family has little money, even the cost of gasoline for a car trip is out of reach. About 65 percent of all household heads took an airplane trip or a rail, bus or car trip of 200 miles or more in 1972-73. Only 40 percent of all poor household heads did so.

Americans averaged about one and a third cars per household in 1973, but the cars were not equally distributed. Some 15 percent of all households had no car at all, while 10 percent had three cars or even more (Table 4-3). Low income families are most likely to do without a car. Car use also is influenced by income; the more money a household has the more the household is likely to drive its car or cars for many thousands of miles every year. The effect of lack of money on car ownership and travel is explored further in Chapter Five, while this chapter focuses on the influences apart from