The U.S. economy and the American way of life rely on transportation— especially the nation’s vast fleet of cars, trucks, and buses. And this transportation depends almost entirely on oil. In 2009, the movement of goods and people in the United States consumed 13 million barrels of oil per day, representing 70% of total U.S. oil consumption and more than twice the amount of crude oil pro- duced domestically. This oil dependence makes the nation vulnerable to supply disruptions and economically harmful price shocks, while petroleum-powered transportation generates air pollution and one third of U.S. greenhouse gas emissions. Reducing transportation’s dependence on oil is vital for achieving U.S. economic and environmental goals.