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Late last month, the Obama administration and 13 automakers announced plans to double the U.S. corporate average fleet economy (CAFE) standard from 27.3 miles per gallon in 2011 to 54.5 mpg by 2025. The new goal will require gradual improvements, beginning in 2017, in the efficiency of passenger cars and light trucks, along with reductions in their greenhouse-gas emissions.

Automotive fuel economy regulations in the United States have rapidly grown more stringent since 2007, when President Bush signed legislation calling for new vehicle fleets to average 35.5 mpg by 2020. (For the previous two decades, the standard held steady at around 25 mpg.) In 2009, the Obama administration moved the target date for 35.5 mpg up to 2016.

Though automakers resisted past increases in the CAFE standard, this time they’ve been much more supportive.  It helps that the administration set less stringent standards for pickup trucks than for passenger cars. And a midterm review is scheduled, to reëvaluate the feasibility of the rules for 2022 to 2025 before finalizing them. Perhaps most important, some experts say, is that there’s enough room for improvements to power trains and auto-body designs—and enough time to make those improvements—that automakers can satisfy the new rules without counting on major technological breakthroughs.

The standard will, in fact, be less stringent than it may seem. Automobile testing takes place in a laboratory, not on the road, so the results need not reflect real-world fuel economy.  The real-world performance will be more like 40 mpg. The actual number will become clearer in September, when the Environmental Protection Agency and the National Highway Transportation Safety Administration release the official details of the plan.

However, it remains a “very challenging target,” says John Heywood, a professor of mechanical engineering at MIT and former director of MIT’s Sloan Automotive Laboratory. Reaching it, he says, will require automakers to make significant changes to the technologies they use and the mix of models they offer consumers. Heywood estimates that up to two-thirds of the required improvement could come through changes to conventional gasoline and diesel engines, increases in the efficiency of hybrids, and greater market penetration of hybrids.

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Credit: Fabrizio Salvetti, under Creative Commons

Tagged: Energy, emissions, hybrid, fuel economy, vehicles, fuel standards

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