Transportation is a complex sector composed of light duty, medium duty, heavy duty, and non-highway vehicles; rail; aircraft; and ships used for personal transport, movement of goods, construction, agriculture, and mining as well as associated infrastructure. Transportation accounts for approximately 10% of gross domestic product (GDP) and depends on significant public sector investment for construction and maintenance of roads, traffic management, transit, airports, ports, and waterways. Transportation uses 27 quadrillion British thermal units (Btu) of petroleum annually, representing 70% of U.S. petroleum use, and 92% of energy for transportation is from petroleum, which means that any strategy to improve our economic and energy security by reducing our dependence on petroleum must include transportation.

The need for a safe, energy-efficient, operationally efficient, low emission, and flexible transportation system can be addressed by advancing technology throughout the transportation system. The need to address energy security concerns, oil import costs, and emissions has long been a national priority driving the Department of Energy’s (DOE) transportation technology research on efficient vehicle drivetrains, including efficient combustion vehicles, plug-in electric vehicles, and fuel cell vehicles. Future personal vehicle markets—in which these efficient vehicle technologies compete—may be transformed by information technologies as well as by social and demographic trends. Technologies, including plug-in electric vehicles and fuel cell vehicles, offer the potential for integration between other energy systems such as electricity and buildings, which could be pursued to improve economy-wide efficiency and reduce emissions. This chapter focuses mainly on technologies applicable to light and heavy duty road vehicles, and surveys other modes and systems-level technologies considerations that could improve energy use across the transportation system.