Transportation is thus an important part of the US energy story. Hidden Costs of Transportation Tailpipe air pollution is only one part of the environmental impacts of the automobile. Burning gasoline emits carbon dioxide, one of the major heat-trapping gases responsible for global warming. Building cars requires extracting steel and aluminum, glass, and petrochemicals. Providing roads, parking lots, driveways, and other supporting structures destroys farmland and habitat.
Suburban sprawl is a direct result of plentiful cars, subsidized roads, and cheap gasoline.
The eight million cars that are junked each year are partly recycled, but also create large hazardous waste problems. Many of the worst effects come from the automobile's use of energy. Between 1973 and 1993 there were over 200,000 oil spills in US waters, spilling over 230 million gallons of oil. Oil refineries are a major source of air and water pollution. The underground storage tanks at gas stations leak, contaminating groundwater.