Improving Energy Efficiency and Limiting Greenhouse Gas Emissions

While the nation considers various options for identifying and providing new energy supplies, opportunities exist to reduce the demand for existing sources of energy and the impact of greenhouse gas emissions from those sources in the transportation sector. The U.S, the Environmental Protection Agency (EPA) estimates that the transportation sector contributes about 27 percent of the nation's total greenhouse gas (GHG) emissions, with roughly two-thirds from cars and light trucks. In addition, while the aviation sector contributes a relatively small amount (about 3 percent) of U.S. GHG emissions, many experts expect these emissions to grow along with the growth of air travel and the increasing efficiency of other industries and modes of transportation.

Programs to reduce the use of traditional energy sources and associated GHG emissions include the efforts of multiple federal agencies, including the National Highway Traffic Safety Administration (NHTSA) within the Department of Transportation (DOT), EPA, Department of Energy (DOE), and Department of Defense. These agencies play a key role by, among other things, establishing national standards and incentives for efficiency, sponsoring research and development, and adopting their own energy savings goals. For example, NHTSA and EPA are setting harmonized standards to increase the fuel economy of cars and reduce carbon dioxide emissions. Also, the Air Force is conducting research into more fuel-efficient engines through a joint effort with engine manufacturers that Air Force officials told us is expected to have commercial applications. Further, an executive order instructs federal agencies to use plug-in hybrid electric vehicles once they become commercially available and comparable with other vehicles on a life-cycle cost basis.

^ Back to topWhat Needs to Be Done

• To help ensure the nation's fuel-saving goals are achieved in the timeliest and efficient fashion, GAO has recommended that NHTSA analyze the need for enhancements to the Corporate Average Fuel Economy program, which requires cars and light trucks to meet certain fuel economy standards. While NHTSA has added credit trading provisions to its most recent proposed rulemaking on fuel economy standards, other enhancements might further the goals of the program. GAO has also recommended that NHTSA, in coordination with other relevant agencies, including EPA and DOE, evaluate policies meant to reduce fuel consumption to ensure they are achieving stated goals.

  Highlights of GAO-07-921 (PDF)

• To help agencies decide what technology to adopt to reduce energy use and emissions, GAO has recommended that DOE—in consultation with other agencies—propose legislative changes to resolve conflicts among energy and vehicle acquisition requirements. GAO also recommended DOE and the General Services Administration provide guidance to help agencies make decisions about acquiring plug-ins.

  Full Report of GAO-09-493 (PDF)

^ Back to topKey Reports

Federal Energy and Fleet Management

Aviation and Climate Change

Vehicle Fuel Economy

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