Larger sport utility vehicles and pickup trucks weighing more than 8,500 pounds when loaded, like many Hummers and Ford Excursions, have been exempt from the regulations. When the system was created, vehicles of that weight were generally used for commercial purposes, but now hundreds of thousands sold each year are intended for family use.

Automakers have had powerful incentives to produce such vehicles because they are exempt from fuel regulations, have had rich profit margins, and many consumers can claim tax breaks for them. The administration had suggested including larger S.U.V.'s in fuel economy regulations in a first wave of proposals in December 2003, but domestic automakers objected that such a move would harm their fragile bottom lines.

Gasoline prices have become a powerful counterweight to regulatory benefits given the biggest gas guzzlers. Many automakers, seeing the weakness in sales of large S.U.V.'s this year - they have recovered only after heavy discounting - are re-emphasizing plans for smaller, lighter S.U.V.'s in the future.

Under the Bush administration plan, about half a dozen size classes will be determined by the vehicle's length and width. Instead of an overall mileage requirement for the total fleet of light trucks a manufacturer sells in a model year, makers will have to meet some kind of target or average within each size class. As a result of the proliferating categories, it will probably become more difficult to predict fuel economy trends.

"It's an invitation to game the system and increase our oil dependence and the pollution that results," said Dan Becker, a global warming strategist at the Sierra Club. "The Bush administration is failing to use the most powerful weapon in its arsenal to save people money at the pump."

Gloria Bergquist, a spokeswoman for the Alliance of Automobile Manufacturers, a lobbying group for General Motors, Toyota and several other producers, said: "The one thing we haven't heard is what the values will be for the different categories, and that will really tell us what the system means.

"Once the proposal comes out, we will have to take a hard look at it and see what the benefits may be to improving fuel economy."

The administration has taken some steps to increase fuel regulations for light trucks, raising the mileage standard for trucks to 22.2 miles a gallon for 2007 models, from 20.7 miles a gallon in 2004 models. Environmentalists have argued that gains from that move were offset by credits given to automakers for making vehicles that can use ethanol, even though there are few gas stations that carry the required blend.

Under the administration's plan, for 2008 to 2010 models automakers will have a choice of complying with the new size-based system or the current system, though a further increase beyond 22.2 miles a gallon is expected in the current system. After 2010, the current system will be eliminated.

__________________
...Tracy

'00 ML320 "Casper"
'92 400E "Stella"