Green Cities
Carbon Pollution, Climate Policy, and the Built Environment: Transportation
August 19, 2013
As part of the Carbon Pollution, Climate Policy, and the Built Environment blog series, this entry focuses on the U.S. transportation sector, the second largest source of greenhouse gas (GHG) emissions in the U.S. In 2011, 28% of the total U.S. GHG emissions came from transportation, primarily from carbon dioxide emissions from fuel combustion in motor engines. GHG emissions from transportation increased 19% between 1990 and 2010. A national inventory report suggests that the emissions increase from this sector was due primarily to the increase in the amount of vehicle miles traveled (VMT) over this period.
The EPA suggests that much of the increase is the result of outward growth of cities and towns and the roads built to serve the new development. Development has become more dispersed since the 1950s, resulting in the increased distances between destinations. At the same time, the design of communities has changed to accommodate more cars. The combination of these two changes has made it impractical or impossible for many people to get around without a car, further encouraging community designs that preclude other choices. While the population roughly doubled between 1950 and 2011, vehicle travel increased nearly six-fold during the same period.
