There is general scientific agreement that greenhouse gas GHG emissions are contributing to a long-term warming trend of the earth, and there is an increasing realization that transportation, as a significant contributor of GHGs, plays an important role in climate change policy and program decisions. Since 1990, transportation has been one of the fastest-growing sources of GHGs in the United States. In fact, the rise in transportation emissions represents 48% of the increase in total U.S. GHGs since 1990. In 2009, the transportation sector directly accounted for about 27% of total U.S. GHG emissions, making it the second largest source of GHG emissions, behind only electricity generation (33%). Nearly 97% of transportation GHG emissions came through direct combustion of fossil fuels.
The prospect of global warming and increased climate variability has become a major policy issue during the last decade. Since transportation is a major-and growing-contributor to GHG emissions, transportation agencies will increasingly seek ways to address it by developing ways to mitigate GHG emissions. This will be especially challenging because agencies simultaneously face reduced revenue, increased congestion, and growing demands for transportation. Therefore, agencies will need guidance and information in order to meet climate change mitigation goals amid these other challenges.
This report, sponsored by the Federal Highway Administration (FHWA), helps address that need. It presents the results of a literature review of GHG mitigation strategies, summarizing what has been published about the GHG effects of different strategies, their costs, and the social feasibility of implementing them. This report does not endorse or recommend particular strategies and did not involve a direct analysis of strategies; therefore, it is best thought of as a sourcebook of information. This information can be used by transportation agencies-principally Departments of Transportation (DOTs) and Metropolitan Planning Organizations (MPOs)-to inform decision-making about strategies in their own jurisdictions. This document may also be of interest to other government agencies, researchers, transportation consultants, and students.