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Climate Change

Sources of Greenhouse Gas Emissions

Transportation Sector Emissions

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Total U.S. Greenhouse Gas Emissions by Economic Sector in 2011
Pie chart of total U.S. greenhouse gas emissions by economic sector in 2009. 34 percent is from electricity, 27 percent is from transportation, 20 percent is from industry, 11 percent is from commercial and residential, and 7 percent is from agriculture.

Total Emissions in 2011 = 6,702 Million Metric Tons of CO2 equivalent
* Land Use, Land-Use Change, and Forestry in the United States is a net sink and offsets approximately 14% of these greenhouse gas emissions.
All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011

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The Transportation sector includes the movement of people and goods by cars, trucks, trains, ships, airplanes, and other vehicles. The majority of greenhouse gas emissions from transportation are CO2 emissions resulting from the combustion of petroleum-based products, like gasoline, in internal combustion engines. The largest sources of transportation-related greenhouse gas emissions include passenger cars and light-duty trucks, including sport utility vehicles, pickup trucks, and minivans. These sources account for over half of the emissions from the sector. The remainder of greenhouse gas emissions comes from other modes of transportation, including freight trucks, commercial aircraft, ships, boats, and trains as well as pipelines and lubricants.

Relatively small amounts of methane (CH4) and nitrous oxide (N2O) are emitted during fuel combustion. In addition, a small amount of hydrofluorocarbon (HFC) emissions are included in the Transportation sector. These emissions result from the use of mobile air conditioners and refrigerated transport.

In 2011, greenhouse gas emissions from transportation accounted for about 28% of total U.S. greenhouse gas emissions, making it the second largest contributor of U.S. greenhouse gas emissions after the Electricity sector. Greenhouse gas emissions from transportation have increased by about 18% since 1990. This historical increase is largely due to increased demand for travel and the stagnation of fuel efficiency across the U.S. vehicle fleet. The number of vehicle miles traveled by passenger cars and light-duty trucks increased 34% from 1990 to 2011. The increase in travel miles is attributed to several factors, including population growth, economic growth, urban sprawl, and low fuel prices over much of this period. Between 1990 and 2004, average fuel economy among new vehicles sold annually declined, as sales of light-duty trucks increased. However, new vehicle fuel economy began to improve in 2005, largely due to a lower light-duty truck market share and higher fuel economy standards.

To learn about projected greenhouse gas emissions to 2020, visit the U.S. Climate Action Report 2010 (PDF). (193 pp, 3.1 MB)

Greenhouse Gas Emissions from Transportation
Line graph of greenhouse gas emissions from transportation for 1990 to 2009. The greenhouse gas emissions started just above 1,500 million metric tons of carbon dioxide equivalents in 1990, and rose to a peak of just below 2,000 million around 2007. At the end of the time span, the line starts to dip and ends around 1,800 million metric tons of carbon dioxide equivalents in 2009.

Note: Emissions involved in the consumption of electricity for transportation activities are included above, but not shown separately (as was done for other sectors). These indirect emissions are negligible, accounting for less than 1% of the total emissions shown in the graph.
Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011.

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Reducing Emissions from Transportation

There are a variety of opportunities to reduce greenhouse gas emissions associated with transportation. The table shown below categorizes these opportunities and provides examples. For a more comprehensive list, see Chapter 5 of the Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change . Link to EPA's External Link Disclaimer

Examples of Reduction Opportunities in the Transportation Sector
Type How Emissions are Reduced Examples
Fuel Switching Using fuels that emit less CO2 than fuels currently being used. Alternative sources can include biofuels; hydrogen; electricity from renewable sources, such as wind and solar; or fossil fuels that are less CO2-intensive than the fuels that they replace.
Learn more about Alternative and Renewable Fuels.
  • Using public buses that are fueled by compressed natural gas rather than gasoline or diesel.
  • Using electric or hybrid automobiles, provided that the energy is generated from lower-carbon or non-fossil fuels.
  • Using renewable fuels such as low-carbon biofuels.
Improving Fuel Efficiency with Advanced Design, Materials, and Technologies Using advanced technologies, design, and materials to develop more fuel-efficient vehicles.
  • Developing advanced vehicle technologies such as hybrid vehicles and electric vehicles, that can store energy from braking and use it for power later.
  • Reducing the weight of materials used to build vehicles.
  • Reducing the aerodynamic resistance of vehicles through better shape design.
Improving Operating Practices Adopting practices that minimize fuel use.
Improving driving practices and vehicle maintenance.
Learn about how the freight transportation industry can reduce emissions through EPA's SmartWay Program.
  • Reducing the average taxi time for aircraft.
  • Driving sensibly (avoiding rapid acceleration and braking, observing the speed limit).
  • Reducing engine-idling.
  • Improved voyage planning for ships, such as through improved weather routing, to increase fuel efficiency.
Reducing Travel Demand

Employing urban planning to reduce the number of miles that people drive each day.
Learn about EPA's Smart Growth Program.

Reducing the need for driving through travel efficiency measures such as commuter, biking, and pedestrian programs.
See a list of links to state, local, regional travel-efficiency programs.

  • Building public transportation, sidewalks, and bike paths to increase lower-emission transportation choices.
  • Zoning for mixed use areas, so that residences, schools, stores, and businesses are close together, reducing the need for driving.

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