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In the United States we use 28% of our energy to move people and goods from one place to another. The transportation sector includes all modes of transportation—from personal vehicles (cars, light trucks) to public transportation (buses, trains) to airplanes, freight trains, barges, and pipelines. One might think that airplanes, trains, and buses would consume most of the energy used in this sector but, in fact, their percentages are relatively small—about 9% for aircraft and about 3% for trains and buses. Personal vehicles, on the other hand, consume more than 60% of the energy used for transportation.
Over the past century, dependence on vehicles burning petroleum-based fuels has become a defining component of American life, bringing countless benefits. In fact, the United States, with less than 5% of the world’s population, is home to one-third of the world’s automobiles. In 2007, automobiles, motorcycles, trucks, and buses drove nearly 3 trillion miles in our country—about the equivalent of driving to the sun and back 13,440 times. Over the next 20 years, the total number of miles driven by Americans is projected to grow by 40%, increasing the demand for fuel.
Over the next 20 years, the total number of miles driven by Americans is projected to grow by 40%, increasing the demand for fuel.
86% of all the energy used in this sector comes from gasoline and diesel fuels, a troubling fact. Combustion of gasoline and diesel fuel emits carbon dioxide, as well as particulate matter, oxides of nitrogen (a prime component of “smog”), carbon monoxide, and unburned hydrocarbons. Indeed, whenever any fossil fuels are burned, carbon dioxide is released into the atmosphere, where it functions as a heat-trapping greenhouse gas. Also of concern is that we are dependent on foreign sources for two-thirds of our oil supplies.
Efforts are already well under way to find suitable alternatives to oil. Biofuels are one possibility. Alternative types of vehicles—hybrids, electric vehicles, and vehicles powered by hydrogen fuel cells, for example—all have the goal of reducing our dependence on oil. Petroleum sources that could serve as alternatives to conventional oil, such as oil shale and tar sands, could reduce our dependence on foreign oil, but wouldn’t help solve the environmental issues surrounding burning fossil fuels. Mining these resources can have damaging environmental effects, as well. Converting coal to liquid fuel is another option but it, too, has significant implications on the environment. The AEF committee estimates that the coal-to-liquid plants could replace up to 3 million barrels of gasoline per day by 2035 but that would require a 50% increase in U.S. coal production.
Greater vehicle efficiency may be our greatest short term strategy for reducing demand for petroleum. The CAFE standards, initially adopted in 1975, made more stringent in 2007, and strengthened again in pending legislation, require automobile manufacturers to build cars with higher average fuel economy.
Explore Our Energy System to see how the transportation sector fits in with the rest of the energy flow in the United States.