The increase in atmospheric greenhouse gas (GHG) levels caused by the increased use of fossil fuels for energy services, in particular transport, heating and electricity generation, is known to be a major driver of climate change. The United States is responsible for a quarter of the world's total greenhouse gas emissions, represents only 5% of the world's population, and becomes the world's largest emitter of atmospheric greenhouse gases (EPA, 2011). Since 1970, the U.S. share of net crude oil imports and consumption has increased significantly, and most imported liquid-based petroleum fuels have been used for the U.S. transportation sector (EIA, 2010). Today, in the United States, transportation is the second largest source of final energy sector emissions (CO2), after the electric power sector. In 2008, the US transportation sector becomes the largest contributor of CO2 emissions, accounting for 95% of CO2 emissions. Greenhouse gas emissions from US transportation account for one-third of total US greenhouse gas emissions (EPA, 2011). In the same year, the U.S. light transportation sector, including passenger cars and light trucks, consumed approximately 60% of total liquid-based petroleum fuel supplies (EIA, 2010). Due to the carbon-intensive fossil fuel energy supply, greenhouse gas emissions from light-duty vehicles account for approximately 40% of total U.S. transportation greenhouse gas emissions (EIA, 2010). Over the next few decades, demand for liquid-based petroleum fuels needed for light transportation is expected to grow rapidly (EIA, 2010). Due to the increase in gasoline consumption for internal engine combustion, an increase in G...... middle of paper ......p://www.fueleconomy.gov/feg/ noframes/ 31016.shtmlUNEP. (2009). Hybrid electric vehicles: an overview of current technology and its application in developing and transition countries. Nairobi, Kenya: United Nations Environment Programme.US DOT. (2003, October). OmniStats - On a typical day, how many miles do you travel one way from home to work? Retrieved October 12, 2011, from Research and Innovative Technology Administration (RITA): http://www.bts.gov/publications/omnistats/volume_03_issue_04/html/figure_02.htmlUS OPM. (2011). Federal Holidays 2011. Retrieved October 1, 2011, from U.S. Office of Personnel Management: http://www.opm.gov/operating_status_schedules/fedhol/2011.aspWeisser, D. (2007). A guide to life cycle greenhouse gas (GHG) emissions from electricity supply. Austria: Economic and Planning Studies Section, International Atomic Energy Agency.