1 Teragrams of CO2 equivalent—1 TgCO2 Eq = 1 million metric ton of carbon equivalent x (44/12). A teragram = 1 trillion grams.
2 "Other" carbon dioxide emissions are from motorcycles, construction equipment, agricultural machinery, pipelines, and lubricants.
NOTE: Highway includes passenger cars, buses, light-duty trucks, and other trucks.
SOURCE: U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2001 (Washington, DC: April 2003), table 1-14, also available at http://www.epa.gov, as of June 2003.