Study examines transportation’s role in reducing U.S. GHG emissions

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A number of strategies can be used to reduce greenhouse gas emissions from transportation, such as using low-carbon fuels, increasing vehicle fuel economy, improving system efficiency and reducing travel that involves high levels of carbon emissions, according to a report released Thursday, April 22, by the U.S. Department of Transportation.

“Reducing the greenhouse gas emissions that contribute to global climate change is one of the great challenges of our time,” says U.S. Transportation Secretary Ray LaHood. “Transportation is one of the major contributors to greenhouse gases, and the transportation sector must be a big part of the solution. This report provides valuable information that will help us in our effort to protect the environment.”

According to the report, 29 percent of all U.S. greenhouse gas emissions and 5 percent of global emissions are due to burning fuel to power U.S. vehicles. The majority of these emissions, totaling 59 percent, come from light-duty vehicles, followed by freight trucks at 19 percent and aircraft at 12 percent. Between 1990 and 2007, greenhouse gas emissions from U.S. transportation increased 27 percent and accounted for almost one-half of the total national increase during that period.

The report, while making no specific recommendations, analyzes the full range of strategies available to reduce transportation’s greenhouse gas emissions. Among specific findings:
• More fuel-efficient gasoline vehicles could reduce per-vehicle emissions by 8 to 30 percent, hybrid vehicles 26-54 percent, and plug-in hybrids 46-75 percent;
• More direct routing of airline flights using NextGen technology and more efficient takeoffs and landings could reduce aviation greenhouse emissions by up to 10 percent by 2025; and
• Reducing the number of vehicle-miles traveled through a combination of strategies, including improved public transportation, coordinated transportation and land use strategies, and greater opportunities for walking and biking – practices emphasized in DOT’s livability initiative – could reduce transportation greenhouse emissions 5 to 17 percent by 2030.

The report also discusses policy options for implementing these strategies, such as efficiency standards, transportation planning and investment, market-based incentives, research and development, and economy-wide carbon policies. DOT already has begun work in these areas.

“Earlier this month, we established historic new fuel economy standards that will save nearly a billion tons of greenhouse gas emissions over the lives of the vehicles covered,” LaHood says. “In aviation, DOT has put energy and environmental concerns at the heart of NextGen – the initiative to modernize the U.S. air traffic system. The department’s Sustainable Communities Partnership with EPA and HUD is providing low-carbon transportation options.”

The report, “Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions,” was mandated by the Energy Independence and Security Act of 2007. It is available at