Virtually all human activities have an impact on our environment, and transportation is no exception. While transportation is crucial to our economy and our personal lives, the environmental impacts of transportation are equally significant and wide-ranging.
Transportation specifically contributes to global warming through the burning of gasoline and diesel fuel. Any process that burns fossil fuel releases carbon dioxide, a greenhouse gas, into the air. Based on global warming potential, carbon dioxide accounts for over 80 percent of total greenhouse gas emissions in the United States. In 1997, transportation sources emitted approximately 31 percent of carbon dioxide from fossil fuel combustion (or 460.4 million metric tons of carbon) in the United States.
In contrast with trends in other air emissions, greenhouse gas emissions from transportation continue to rise – in large part because travel growth has outpaced improvements in vehicle energy efficiency. However, while vehicles continue to become more efficient, there are plenty of transportation alternatives that can be pursued to help slow the growth in vehicle miles traveled.
For Additional Information
Municipal Actions – Transportation
Cities and towns are in the position to take a variety of energy efficiency and renewable energy actions that can have multiple benefits including saving money, creating jobs, promoting sustainable growth, and reducing criteria pollutants. Find out what some municipalities are doing about climate change in the area of transportation.
Fuel Economy Site 
Sponsored by the Department of Energy and the Environmental Protection Agency, the Fuel Economy Web Site is designed to help the public factor energy efficiency into their car buying decisions. This site offers information on the connection between fuel ecocomy, advanced technology, and the environment.
EPA's Office of Transportation and Air Quality
Formerly the Office of Mobile Sources, EPA's Office of Transportation and Air Quality protects public health and the environment by controlling air pollution from motor vehicles, fuels, and nonroad equipment, and by encouraging travel choices that minimize emissions.
DOE's Clean Cities Program
Clean Cities is a program sponsored by the U.S Department of Energy which is designed to encourage the use of alternative fuel vehicles (AFVs) and their supporting infrastructure throughout the nation. By encouraging AFV use, the Clean Cities program will help achieve energy security and environmental quality goals at both the national and local levels.
Unlike traditional command-and-control programs, the Clean Cities program takes a unique, voluntary approach to AFV development, working with coalitions of local stakeholders to help develop the AFV industry and integrate this development into larger planning processes.