U.S. DEPARTMENT OF TRANSPORTATION
Executive Summary
INTRODUCTION
This study evaluates potentially viable strategies to reduce transportation greenhouse gas (GHG) emissions. The study was mandated by the Energy Independence and Security Act (P.L. 110140, December 2007). The Act directed the U.S. Department of Transportation (DOT), in coordination with the U.S. Environmental Protection Agency (EPA) and consultation with the U.S. Global Change Research Program (USGCRP), to conduct a study of the impact of the Nation’s transportation system on climate change and strategies to mitigate the effects of climate change by reducing GHG emissions from transportation. This study also examines the potential impact of these strategies on air quality, petroleum savings, transportation goals, costs, and other factors. Each GHG reduction strategy may have various positive impacts (including cobenefits) or negative impacts on these factors. Potential tradeoffs and interdependencies when reducing GHG emissions will need to be considered in order to develop balanced solutions.
This study does not take a position as to which strategy, or collection of strategies, should be adopted to accomplish the Nation’s clean energy and GHG reduction goals. Rather, the study attempts to objectively examine numerous proposed strategies and assess their potential to reduce transportation GHG emissions. The assessments are based on published scientific literature, current policy studies, and best professional estimates. Each strategy is assessed relative to projections of future transportation GHG emissions based on U.S. Energy Information Administration Annual Energy Outlook (AEO) estimates.
The study is presented in two parts: Volumes 1 and 2. Volume 1: Synthesis Report provides an overview of the study’s findings and discusses policy options that Congress may wish to consider to reduce transportation GHG emissions. Volume 2: Technical Report provides the technical details of the assessment.
GREENHOUSE GAS EMISSIONS AND GLOBAL CLIMATE CHANGE
The Intergovernmental Panel on Climate Change (IPCC) estimates that in the absence of additional climate policies to reduce GHG emissions, baseline global GHG emissions from human sources will increase between 25 percent and 90 percent between 2000 and 2030, with CO2 emissions from energy use growing between 40 and 110 percent over the same period. The IPCC projects that global temperatures will rise between 2°F to 11.5°F by 2100, and global sea level will rise between 7 to 23 inches. More recent estimates that include the effects of polar ice sheet melting suggest a possible 3 to 4 foot sea level rise. According to the Intergovernmental Panel, global GHG emissions must be reduced to 50 to 85 percent below year 2000 levels by 2050 to limit warming to 2.0°C to 2.4°C (3.6°F to 4.3°F). To reach this target, GHG emissions from all sectors must be reduced through a multigenerational effort.
U.S. TRANSPORTATION GREENHOUSE GAS EMISSIONS
The primary greenhouse gases produced by the transportation sector are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and hydrofluorocarbons (HFC). Carbon dioxide, a product of fossil fuel combustion, accounts for 95 percent of transportation GHG emissions in the United States.
Transportation GHG emissions account for 29 percent of total U.S. GHG emissions, and over 5 percent of global GHG emissions. Except otherwise noted, the estimates in this report account for “tailpipe” emissions from burning fossil fuels to power vehicles and do not account for greenhouse gases emitted
through other transportation lifecycle processes, such as the manufacture of vehicles, the extraction and refining of fuels, and the construction and maintenance of transportation infrastructure. Including these processes, U.S. transportation lifecycle greenhouse gases are estimated to account for about 8 percent of global GHG emissions.
Transportation GHG emissions have been growing steadily in recent decades. From 1990 to 2006 alone, transportation GHG emissions increased 27 percent, accounting for almost onehalf of the increase in total U.S. GHG emissions for the period.
In 2006, emissions from onroad vehicles accounted for 79 percent of transportation GHG emissions. Emissions from lightduty vehicles, which include passenger cars and light duty trucks (e.g., sport utility vehicles, pickup trucks, and minivans) accounted for 59 percent of emissions. Emissions from freight trucks accounted for 19 percent, and emissions from commercial aircraft (domestic and international) for 12 percent. Emissions from all other modes accounted for less than 10 percent of total emissions.
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Tags: Department of Transportation, DOT, Emissions, Federal Transit Administration, FTA, Pollution, US DOT