The Bush administration proposed to overhaul federal vehicle fuel economy regulations on Dec. 22 for the first time since they were created after the oil shocks of the 1970s. But it is not clear to what extent, if at all, the proposals -- which are aimed at sport utility vehicles, pickup trucks and minivans -- would reduce gasoline consumption or save lives, two of the main stated goals of the program, according to the New York Times. The proposals, which appear in a report released by the National Highway Traffic Safety Administration (NHTSA), conform to earlier reports about the administration's plans on fuel economy, and the main tenets have been known since March, according to the Times. The proposed changes would break the light truck fleet into either weight or size classes instead of having a single fleetwide average for all light trucks; they also might regulate light trucks that weigh more than about 5,000 pounds more stringently. Much will depend on how many weight or size classes there are and how challenging the mileage targets are for each class, the Times said. The report conceded that such a plan would not necessarily improve fuel economy. "It is theoretically possible the overall fuel economy of the fleet would not increase significantly or might even decline," the report said. But the proposal would bring the largest sport utilities, those over roughly 6,000 pounds unloaded, into the regulatory system for the first time, according to the Times. "It's really a safety proposal," said NHTSA administrator Dr. Jeffrey W. Runge, adding that improving fuel economy and energy security was a goal of the plan, but secondary to safety. "They've painted some broad strokes, but we need to see the fine print," said Eron Shosteck, a spokesman for the Alliance of Automobile Manufacturers. "We can't give a detailed assessment until we see a detailed proposal."