BALTIMORE -- It's official: Automakers must increase average light-truck fuel economy by more than 10 percent over the next five years.

The Bush administration adopted regulations on Wednesday that establish light-truck fuel economy standards for the 2008-11 model years. By the end of that period, trucks must average about 24 mpg.

The standard for 2006 is 21.6 mpg; and for 2007, 22.2 mpg. Those levels were set in early 2003. The car standard remains at 27.5 mpg.

As expected, the rules include a provision to vary the standards according to the sizes of vehicles. Bigger trucks will have less stringent standards. Smaller trucks will have tougher standards.

The size provision is the biggest structural change in the 30-year-old corporate average fuel economy, or CAFE, program. The change is expected to reduce automaker incentives to downsize vehicles and potentially make them less safe.

It also means that by 2011, each car company will have its own fuel economy standard based on its product mix.

The provision is widely viewed as a break for General Motors, Ford Motor Co. and the Chrysler group, which rely more on larger trucks for sales and profit. But Toyota and Nissan have been expanding their offerings of larger trucks.

Transportation Secretary Norman Mineta announced the adoption of the CAFE rules at the Baltimore Ravens' football stadium. The stadium overlooks Interstate 395, a branch of the East Coast's most heavily traveled corridor.

"The new standards represent the most ambitious fuel economy goals for light trucks ever developed" in CAFE's history, Mineta said in a statement.

Among the key provisions:

* Manufacturers’ truck fleets will have to average 22.5 mpg in 2008, 23.1 mpg in 2009, and 23.5 mpg in 2010.

* By 2011, all automakers will use the size-based system.

* For the first time, fuel economy standards apply to some trucks with gross weights of more than 8,500 pounds. Pickups and cargo vans of that size remain exempt.



During the public-comment period on the administration's new rules, automakers called them challenging. But some companies acknowledged they will be able to comply using available technology.

Environmental groups argued that much tougher standards are needed.

WASHINGTON -- The Bush administration insists that its new fuel economy rules will force SUVs, pickups and minivans to get better gasoline mileage. But skeptics wonder whether the Law of Unintended Consequences will overtake that goal.

Critics say the new standards could encourage automakers to build bigger trucks, potentially wiping out the promised fuel savings. That's because the standards set different fuel economy targets for different-sized light trucks.

The classifications are based on the area bounded by a truck's four wheels, called its "footprint." The bigger the footprint, the lower the mileage requirement.

The new rules also impose a unique fuel economy standard on each automaker, based on its product mix. They amount to the biggest structural change in the 30-year history of the federal corporate average fuel economy, or CAFE, program.

For example, the rules set a target for the Hummer H3 of 24.16 mpg by the 2011 model year. That's 4 mpg more than the EPA estimate of the H3's current fuel economy. Such an improvement likely would require changes in the H3's powertrain, aerodynamics and weight.

But if Hummer were to add two inches of track width and four inches of wheelbase to the H3, the vehicle's fuel economy target would drop by about 1 mpg.

Claybrook weighs in

"The complex new sliding scale and the secrecy of automakers' product plans will submerge any accountability for achieving fuel savings in an oil slick of confusion," says Joan Claybrook, president of the consumer group Public Citizen and a former head of the National Highway Traffic Safety Administration.

The new rules, she says, give car companies an incentive "to cut out more efficient vehicles altogether."

John Johnson is an engineering professor at Michigan Technological University. He sat on a National Research Council panel that in 2001 proposed changes to CAFE along the lines that U.S. Transportation Secretary Norman Mineta announced last week.

Johnson says he doesn't advocate manipulation of truck sizes but expects that to happen. That is how automakers respond to regulation, he says.

"You try to figure out how to optimize the rules for you," Johnson told Automotive News.

The new standards for light trucks will take effect for the 2008 model year. Overall, they require fuel economy improvements of about 10 percent, to an average of 24 mpg in 2011.

For 2006, the light-truck standard is 21.6 mpg; for 2007 it's 22.2 mpg. The car standard stays at 27.5 mpg.

A Ford Escape, with a footprint of 43.5 square feet, will have a fuel economy target of 27.32 mpg, NHTSA says. A Ford F-150 SuperCab, with a footprint of 75.8 square feet, has a target of 21.81 mpg.

NHTSA projects that BMW, which mostly builds small and medium-sized SUVs, will have to meet a 2011 truck fleet standard of 25.8 mpg. For General Motors, which makes more large trucks, the standard would be 23.2 mpg.

No backstop

Roland Hwang, vehicles policy director of the Natural Resources Defense Council, says his group and others asked Bush administration officials for a "backstop" provision. It would have required a certain level of improvement by each automaker, regardless of product mix.

"They rejected that, of course," Hwang says. With lax standards and no backstop, he says, "there is a danger and an incentive to continue to upsize the fleet."

Chris Preuss, GM's public policy spokesman, says his company is unlikely to enlarge vehicles just to meet the new fuel economy standards. He notes that automakers will not have to make every vehicle hit its CAFE target.

Instead, Preuss says, fuel economy standards still will be based on averaging. A company can continue to build a higher volume of a vehicle that exceeds its target to offset sales of a vehicle of another size that misses its target, he says.

GM "will meet our obligation" to comply with CAFE, Preuss says.

Acting NHTSA Administrator Jacqueline Glassman estimates that the new rules will add about $200 to the customer's cost of a vehicle in 2011. A consumer would recover that amount in four years from fuel savings, she says.

Steve Kratzke, NHTSA's associate administrator, was a key developer of the regulations. He says there could be safety benefits if automakers move wheels farther out to the corners of new vehicles. Researchers say that vehicles with wider stances are less prone to roll over.