ETROIT, Jan. 27 — Hybrids, vehicles that save gasoline by combining electric motors with internal combustion engines, are emerging as the first alternative-powered cars to show signs of catching on with automakers and some consumers since the automobile's early days.

Toyota and Honda are already selling tens of thousands of hybrids, and General Motors and Ford, worried about ceding another fast-moving market to the Japanese, have announced plans to join them. The hybrid's rise has been encouraged by pressure from environmentalists and regulators, particularly California rules curbing greenhouse gases and smog-forming pollutants.

"Hybrid technology is one that has great appeal because we don't have to really invent anything; we know they work," said William Clay Ford Jr., Ford's chairman, in a recent speech. "If these vehicles don't get customer acceptance, I really don't know what we do next."

Associated Press

A century ago, gasoline-powered Oldsmobiles, like the Runabout, gained popularity and eventually helped to make steam-powered vehicles obsolete.

Reuters

Today, carmakers like General Motors, with its Hy-wire alternative vehicles, say their hybrid cars are catching on.

A hybrid's battery is recharged by the internal combustion engine and by collecting energy when the car brakes. The battery powers an electric motor that supplements, or takes over for, the gasoline-powered engine. In the Honda Civic hybrid, an electric motor assists when the car is climbing hills or accelerating sharply. In the Toyota Prius, the electric motor takes over at low speeds. In both, the gas engine shuts off when the car stops.

Hybrids have until now been something of a curiosity and account for a small fraction of overall sales. Only three models — all small cars — are available, one from Toyota and two from Honda, and they cost a few thousand dollars more than conventional cars. About 150,000 have been sold worldwide since hybrids were introduced in the late 1990's, fewer than the number of vehicles typically produced by a single auto factory in a year.

But carmakers now appear ready for a much broader rollout. Earlier this month, at the North American International Auto Show here, G.M. — previously the industry's most vocal skeptic — publicly embraced the technology. The company said it would sell a hybrid version of its Saturn Vue sport utility vehicle in 2005 that would approach 40 miles a gallon in fuel economy, compared with mileage in the low 20's for current models. G.M. said it would offer vehicles with more limited forms of hybrid power, too, promising 10 to 15 percent improvements in fuel economy on four other models by 2007.

Also at the auto show, the annual beauty pageant where the industry trots out its latest designs and biggest pronouncements, Toyota said it would sell the first luxury hybrid, a Lexus sport utility vehicle, starting next year — part of a plan to sell 300,000 hybrids annually by mid-decade.

Ford plans to sell what will probably be the first hybrid sport utility vehicle, a version of the Escape, at the end of this year, and showed off a new hybrid prototype called the Model U.

Even the Army, which pays as much as $400 a gallon in battlefield fuel costs, had a hybrid on display — a hulking diesel combat vehicle, built by G.M., that is one of several prototypes being considered for service within a few years, including hybrid Humvees.

"You run those things on battery power; there's no noise," said Maj. Gen. Ross Thompson III, the head of the army's Tank, Automotive and Armaments Command, explaining the appeal of hybrids for the military. "For a reconnaissance mission, or if you want to not be noticed, you can use the batteries."

A century ago, in 1903, gasoline-powered Oldsmobiles shouldered past steam-powered Locomobiles to become America's top-selling brand. Never again would electric or steam cars rule the road. There is scant suggestion that hybrids may replace gasoline-powered cars in the same way. Among other things, two motors cost more than one.

But Stephen Girsky, an auto analyst at Morgan Stanley, predicts that hybrids could grow to 10 to 15 percent of American vehicle sales, which approached 17 million last year. Government incentives, gas prices and how much manufacturing costs can be reduced will be important factors, he said.

John Casesa, an analyst at Merrill Lynch, said that because the Japanese "view this as a core technology over the next decade," domestic automakers have to respond. "Inevitably, we're moving toward a future with higher fuel economy standards, risk to energy supplies and higher environmental consciousness," he said. "So there's a market pull here."

In addition to representing a response to the latest competitive threat from Japan, Detroit's hybrid plans are good for public relations, especially as hot-selling sport utility vehicles come under increasing criticism for how much gasoline they consume. A recent ad campaign by an evangelical group suggested that Jesus would find sport utilities morally unfit; another, orchestrated by Arianna Huffington, argued that these vehicles increased American reliance on oil from the Middle East.

But there remains considerable debate within the auto industry about whether hybrid technology is too costly to become universal — and whether its advantages are so modest that it represents a diversion from more worthy approaches to improving fuel economy.

"Right now," said Wolfgang Bernhard, chief operating officer of the Chrysler division of DaimlerChrysler, "everybody is jumping on the hybrid bandwagon and saying this is the most important thing and without it the world's going to end. It reminds me of the hype we had around e-business in the early 90's."

Daimler this year plans to sell a small number of hybrid Dodge Ram pickups tailored for contractors, who could use the trucks as mobile power generators. The company's German executives, though, prefer the updated diesel-engine vehicles already prevalent in Europe; diesels achieve 25 percent better mileage than comparable gasoline-powered cars. American environmentalists, worried about emissions of smog-forming pollutants, oppose a broad reintroduction of diesel-powered vehicles.

To Japanese-based carmakers, the choice is clear from an environmental standpoint. Hybrids are "the solution for today," said James E. Press, executive vice president of Toyota Motor Sales U.S.A.

"What's the cost of fuel?" he said. "It's not $1.80 a gallon. It's how much does a war in Iraq cost? How much does the fact you've got 75 years of this stuff left on the planet cost? And then what's the cost of pollution? At some point, the industry has to recognize it."

Last year, Toyota sold more than 20,000 of its Prius subcompacts, making Prius, which gets about 40 miles per gallon, the best-selling hybrid in the United States.

With a base price of $20,500, a Prius costs about $5,000 more than a Toyota Corolla. That is a considerable gap, though Prius buyers can take a $2,000 income tax deduction. Toyota says it now makes some profit on each Prius it sells, if the research-and-development costs are not factored in, but the company will not say how much less profitable hybrids are than its conventional vehicles.

Toyota executives insist that the cost differential can be brought down significantly. For example, Mr. Press said the electric motor in a sport utility vehicle could be configured to power the rear wheels, eliminating the need for, and cost of, a conventional four-wheel-drive system.

In addition, Congress has considered adding more tax benefits for buyers.

Rick Wagoner, G.M.'s chief executive, said such incentives, which could quickly accumulate into a considerable government subsidy, are critical to the future of hybrids, because G.M. does not intend to sell its hybrids at a loss.

"For this to go, it's a team sport," he said. "We're going to need the government in."

G.M.'s hybrid plans were promoted in full-page newspaper ads and greeted as something of a road-to-Damascus conversion. A Sierra Club statement likened the announcement to "Nixon going to China." Nicholas V. Scheele, Ford's chief operating officer, described himself as "baffled," noting that only recently G.M. had dismissed hybrids as too costly.

Lawrence D. Burns, G.M.'s vice president for research and development, attributed the change of heart to the early success of Toyota and Honda and "the uncertain future in 2005 and beyond with regulatory requirements and gasoline prices."

Robert A. Lutz, G.M.'s vice chairman for North American operations, was more blunt. "You just can't fly in the face of public opinion," he told The Detroit News. "It would be self-defeating to constantly say to ourselves, `It's not gonna work, it's not gonna work.' "

Since the days of Thomas A. Edison, the auto industry has been trying to make a credible alternative to the internal combustion engine. Edison himself was a pioneer of the battery-powered car, though he is said to have told a young Henry Ford that his idea for a gasoline engine sounded pretty good.

The first car bought by the government, during Theodore Roosevelt's administration, was a Stanley Steamer, a steam-powered car. In the 1950's, Chrysler was so sure that cars powered by jet engines would be the future that it built a small fleet of them. Today, the industry is convinced that future generations of automobiles will be propelled by hydrogen fuel cells, which generate electricity through a chemical reaction.

If debate continues on hybrids, some clarity is emerging on other alternative technologies. The future seems notably dim for battery powered cars, whose batteries do not last very long and take hours to recharge.

"At the moment I think it's being put to rest," said Fujio Cho, the president of Toyota, adding that his company is "hardly selling any."

Carlos Ghosn, chief executive of Nissan, agreed that battery-powered cars are "completely obsolete," though Nissan continues to lease battery-powered Altra station wagons to California utilities.

Then there is the fuel cell, for environmentalists and even many auto executives the nonpolluting ideal of alternative fuel technologies. Not only did fuel cells power the inside of lunar landers, they emitted water for astronauts to drink. But will they soon supplant the internal combustion engine?

"Today a fuel cell car probably costs about — I'm going to be optimistic — $700,000," Mr. Ghosn said. "We're far from sticker price, eh? We're going to have to get it down to $20,000, $30,000."

ETROIT, Jan. 29 — President Bush's proposal to double federal spending on fuel cell research drew praise today from automakers and skepticism from environmentalists.

"Our scientists and engineers will overcome obstacles to taking these cars from laboratory to showroom so that the first car driven by a child born today could be powered by hydrogen and pollution-free," the president said in his State of the Union address on Tuesday night.

Automakers view the fuel cell as the technology that will eventually supplant the internal combustion engine and silence environmentalists concerned about smog and greenhouse gases. Fuel cells generate electricity from chemical reactions between hydrogen and air. Their only tailpipe emission is water vapor. But energy would be required to produce hydrogen to run tens of millions of cars, and greenhouse gas emissions might be the result, depending on how the hydrogen was produced.

"We think this is a great step in the right direction," said Christopher Preuss, a spokesman for General Motors . "The president showing leadership in hydrogen is critical to making the jump. We're very pleased."

G.M. has built the most Jetsons-like prototype fuel cell vehicle, called the Hy-Wire. All of its drive components are underfoot, there is no dashboard, and the driver uses handgrips instead of foot pedals. Toyota and Honda have already leased the first tiny test fleets of fuel cell vehicles to the University of California and the city of Los Angeles, respectively.

But automakers say the technology is not expected to be ready for broader sale before the end of the decade at the earliest, and many analysts believe that is optimistic. Besides the technological challenges that remain for fuel cells themselves — particularly the challenge of finding a safer way to store hydrogen, which is now stored in highly pressurized tanks — there is the daunting notion of outfitting the nation's filling stations with hydrogen instead of gasoline.

Environmentalists, though enthusiastic about fuel cells in the longer term, want to see more aggressive development of hybrid cars. Those vehicles achieve sharp increases in fuel economy by supplementing gasoline engines with electric motors. General Motors and the Ford Motor Company have said they plan to join Toyota and Honda in equipping some vehicles with the hybrid technology.

"The auto industry is using the promise of future fuel cells as a shield against using existing technology to dramatically cut our oil dependence, and pollution, today," said Daniel Becker, director of the Sierra Club's Global Warming and Energy Program.

Jason Mark, director of the clean vehicles program at the Union of Concerned Scientists, said, "With oil use increasing at alarming rates, President Bush should aggressively push conventional technologies that can deliver cost-effective savings today, as opposed to waiting two decades."

In his speech, President Bush proposed $1.2 billion in additional financing for fuel cell research over five years. Peter Hoffmann, the editor of The Hydrogen and Fuel Cell Letter, said that total federal spending on fuel cells, including military spending, came to about $230 million a year now.

Mr. Hoffmann and others said that the first widespread, practical use of fuel cells was likely to be in consumer electronics. People with cellphones and laptop computers, they said, will be willing to pay extra to avoid the inconvenience of rundown batteries. Next would be technology for houses and commercial sites, which could make all the electricity they needed from fuel cells that drew hydrogen from natural gas.

Cars would be among the most complex applications because operating an ordinary sedan requires about 10 times as many kilowatts of power as a house. Carlos Ghosn, the chief executive of Nissan , quipped earlier this month that a fuel cell car today would have a sticker price of about $700,000.

Jeremy Rifkin, author of The Hydrogen Economy, a recent book extolling the prospects of hydrogen power, dismissed the president's proposal as "a paltry gesture.

"What is required is a government-private partnership on a grand scale with a financial commitment at least equal to the monies currently being spent on homeland security and the preparation for war with Iraq," he said today.

The Bush administration has set in motion regulations to increase by 7 percent the fuel economy of light trucks — sport utilities, pickups and minivans — by the 2007 model year. Regulators are considering further action in later years to narrow the fuel-economy gap between light trucks and cars.

But the administration has also been criticized for a tax provision that would permit small business owners to deduct immediately the entire cost of most of the largest S.U.V.'s, including the BMW X5 and the Hummer H2. The administration has said it is reviewing the loophole.

ETROIT, May 2 — The average fuel economy of the nation's cars and trucks fell to its lowest level in 22 years in the 2002 model year, the Environmental Protection Agency reported today.

The technological and engineering leaps of the last two decades have been poured into everything but fuel economy, according to the agency's statistics. Since 1981, the average vehicle has 93 percent more horsepower and is 29 percent faster in going from 0 to 60 miles an hour. It is also 24 percent heavier, reflecting surging sales of sport utility vehicles.

But over the same period, fuel economy has stagnated, contributing heavily to the nation's rising oil consumption. Cars and light trucks — S.U.V.'s, pickups and minivans — account for about 40 percent of the nation's oil consumption and a fifth of its carbon dioxide emissions, which many scientists see as the leading contributor to global warming.

Light trucks have poorer fuel economy than cars, but the auto industry says it cannot force people to buy more efficient vehicles.

Environmentalists, frustrated by years of legislative defeats and a recent retreat by the Ford Motor Company on a pledge that it would improve the fuel economy of its S.U.V.'s, were further exasperated by the report.

"Without being forced to improve fuel economy by the government, the auto industry doesn't do it," said Daniel Becker, the top global warming expert for the Sierra Club. "Congress has to require energy savings in the energy bill that comes to the floor next week or the auto industry will continue to go in reverse."

The report also said that fuel economy could have improved 33 percent since 1981 if performance and weight of vehicles had been held constant.

But Gloria J. Bergquist, the vice president for communications at the Alliance of Automobile Manufacturers, the industry's chief political lobbying group, said the industry could not force consumers to buy fuel-efficient vehicles.

"We have 30 models that get over 30 miles per gallon, but the top 10 most fuel-efficient vehicles are less than 2 percent of sales," she said. "I would call this report a consumer sales report. It shows what consumers are buying."

In his first speech today as the new chairman of General Motors, Rick Wagoner, who will continue to serve as chief executive, said "the only solution to this tough dilemma of improving fuel economy and reducing emissions in the intensely price-competitive and very low-cost-energy environment here in the U.S. is through technology."

He singled out the potential of hydrogen-powered fuel cells, a clean energy source, which have been a favorite technology of the Bush administration. But many analysts say fuel-cell cars are years, if not decades, away from mass production.

The E.P.A. report came several months later than usual and was somewhat controversial because the agency changed its normal reporting procedures. Instead of reporting only fuel economy changes for the 2002 model year, weighted for sales, the agency also included results for the 2003 model year based on the industry's own sales projections from last September.

By that reckoning, average fuel economy will show its first improvement in more than two decades in the 2003 model year. But the agency said there was a margin for error large enough to swing the results to a loss. And sales trends this year have also not appeared to favor energy conservation.

Light trucks continue to gobble up more of the market than more fuel-efficient passenger cars. Sales of the biggest S.U.V.'s, like the Lincoln Navigator and the Chevrolet Suburban, rebounded from a sluggish first quarter with a strong showing last month.

Further worsening fuel economy statistics are the aggressive moves by Asian automakers into S.U.V.'s of all sizes, with the next battleground being drawn over the last stronghold of Detroit, the pickup truck.

In the 2002 model year, fuel economy averaged 20.4 miles a gallon, the lowest since the fleet averaged 19.2 miles a gallon in 1980. Fuel economy peaked at 22.1 miles a gallon in 1988 but has mostly fallen since.

The agency predicts fuel economy will rise to 20.8 miles a gallon in the 2003 model year, with a 0.5 mile a gallon margin for error. Cars are expected to average 24.8 miles a gallon, compared with 19.6 for minivans, 17.8 for S.U.V.'s and 16.8 for pickups.

David Friedman, a senior policy analyst for the Union of Concerned Scientists, said the report's new methodology "raises a lot of questions."

"I'm very skeptical of their use of the 2003 model year information," he said, adding that "it's difficult to come to any conclusions about any model year before the model year is over."

Conversations with people at the environmental agency who were briefed on the decision to offer 2003 figures indicated that it was not politically motivated but was done in part to prevent news organizations from doing their own projections.

Donald Zinger, the assistant director of the E.P.A.'s office of transportation and air quality, said "some people tried to do it themselves and got all messed up and came out with numbers that were inaccurate."

ASHINGTON, May 27 — Exxon Mobil has publicly softened its stance toward global warming over the last year, with a pledge of $10 million in annual donations for 10 years to Stanford University for climate research.

At the same time, the company, the world's largest oil and gas concern, has increased donations to Washington-based policy groups that, like Exxon itself, question the human role in global warming and argue that proposed government policies to limit carbon dioxide emissions associated with global warming are too heavy handed.

Exxon now gives more than $1 million a year to such organizations, which include the Competitive Enterprise Institute, Frontiers of Freedom, the George C. Marshall Institute, the American Council for Capital Formation Center for Policy Research and the American Legislative Exchange Council.

The organizations are modest in size but have been outspoken in the global warming debate. Exxon has become the single-largest corporate donor to some of the groups, accounting for more than 10 percent of their annual budgets. While a few of the groups say they also receive some money from other oil companies, it is only a small fraction of what they receive from Exxon Mobil.

"We want to support organizations that are trying to broaden the debate on an issue that is so important to all of us," said Tom Cirigliano, a spokesman for Exxon. "There is this whole issue that no one should question the science of global climate change that is ludicrous. That's the kind of dark-ages thinking that gets you in a lot of trouble." He also noted, "These are not single-agenda groups."

The organizations emphasize that while their views align with Exxon's, the company's money does not influence their policy conclusions. Indeed, the organizations say they have been sought out in part because of their credibility. "They've determined that we are effective at what we do," said George C. Landrith, president of Frontiers of Freedom, a conservative group that maintains that human activities are not responsible for global warming. He says Exxon essentially takes the attitude, "We like to make it possible to do more of that."

Frontiers of Freedom, which has about a $700,000 annual budget, received $230,000 from Exxon in 2002, up from $40,000 in 2001, according to Exxon documents. But Mr. Landrith said the growth was not as sharp as it appears because the money is actually spread over three years.

The increase corresponds with a rising level of public debate since the United States withdrew from the Kyoto Protocol, some of the groups said. After President Bush rejected the protocol, a treaty requiring nations to limit emissions of heat-trapping gases, many corporations shifted their attention to Washington, where the debate has centered on proposals for domestic curbs on the emissions.

"Firefighters' budgets go up when fires go up," said Fred L. Smith, the head of the Competitive Enterprise Institute. Myron Ebell, an analyst from the institute, spoke at last year's Exxon shareholders' meeting, where he criticized a renewable energy resolution proposed by a group of shareholders.

Exxon's backing of third-party groups is a marked contrast to its more public role in the Global Climate Coalition, an industry group formed in 1989 to challenge the science around global warming. The group eventually disbanded when oil and auto companies started to withdraw. As companies were left to walk their own path, Exxon shifted money toward independent policy groups.

"Now it's come down to a few of these groups to be the good foot soldiers of the corporate community on climate change," said Kert Davies, a research director for Greenpeace, which has tried to organize an international boycott of Exxon.

Exxon's publicly disclosed documents reveal that donations to many of these organizations increased by more than 50 percent from 2000 to 2002. And money to the American Legislative Exchange Council, a conservative group that works with state legislators, has almost tripled, as the policy debate has moved to the state level.

The gifts are minuscule compared with the $100 million, 10-year scientific grant to Stanford, which is establishing a research center that will focus on technologies that could provide energy without adding to greenhouse gases linked by scientists to global warming. Nevertheless, the donations in the tens of thousands or hundreds of thousands of dollars are significant for groups with budgets ranging from $700,000 to $4 million.

Critics say that Exxon and these groups continue to muddle the debate even as scientific consensus has emerged, and as much of the industry has taken a more conciliatory stance toward the reality of global warming. As Exxon has become isolated from its peers, it has faced increasing pressure from shareholders and environmentalists. BP, Shell and ChevronTexaco have developed strategies that incorporate renewable energy, carbon trading and emissions reductions.

Among the initiatives that Exxon's money has helped is the Center for Science and Public Policy. The two-month-old center is a one-man operation that brings scientists to Capitol Hill on two issues: global warming and the health effects of mercury.

"We don't lobby, we educate," said Bob Ferguson, head of the center, who spent 24 years working as a Republican Congressional staff member. "We try to be nonpolitical and nonpartisan and nonideological."

ETROIT, June 27 — For years, automakers have cited studies contending that thousands of people die annually because fuel economy regulations force the companies to make cars that are not heavy enough.

Larger vehicles, the argument goes, may guzzle more gas but they offer more protection, whether one hits a tree or another car. The argument has been a central one when efforts emerge in Congress to raise fuel economy standards. And it is taken seriously by the Bush administration, which has started an effort to rewrite the fuel economy rules.

The problem with this argument is that it now has little relationship to the American road. As safety advocates point out, the lightest cars have virtually disappeared from American roads over the last 15 years, while the largest vehicles — including sport utilities and pickups — have ballooned, both in number and heft.

The portion of cars that weigh 2,500 pounds or less, which was 18 percent of all passenger vehicles sold in the 1985 model year, has fallen to less than half a percentage point, according to the Environmental Protection Agency. In fact, the average American car has been steadily gaining weight for a decade and a half.

Over the same period, the growth of the largest vehicles has only expanded weight differences that are widely acknowledged to be deadly in collisions. Moreover, the largest vehicles are increasingly not cars but sport utilities and pickups, which ride much higher than cars, increasing the danger to people in cars and the likelihood of deadly rollovers.

When the government created fuel economy regulations after the energy crisis of the early 1970's, few imagined they would become a flashpoint because of an entirely different issue — safety. But the official the Bush administration has chosen to preside over the effort to rewrite the rules, John D. Graham, says saving lives is as important as saving gasoline.

Dr. Graham, the regulations administrator of the Office of Management and Budget, has argued since his years as a Harvard professor and risk expert that fuel regulations have cost thousands of American lives because cars were made too light — in Detroit, the phenomenon is called downsizing. Auto lobbyists have cited Dr. Graham's work, and other research, in opposing tighter fuel standards.

Now Dr. Graham is chairman of an intra-agency group rethinking the fundamental structure of corporate average fuel economy regulations, or CAFE standards, for light trucks — sport utility vehicles, pickups and minivans — for the 2008 model year and beyond. The group also includes the National Highway Traffic Safety Administration, whose chief, Jeffrey W. Runge, will play a central role; the Energy Department; and the E.P.A.

Dr. Graham said in an e-mail exchange that the administration's intention was "to stimulate more fuel-saving, technological innovation while protecting safety and American jobs."

He said he did not want to press automakers to make most light trucks lighter. "CAFE reform does not make sense if it forces consumers to purchase vehicles that are lighter or smaller than they need," Dr. Graham said.

But he also said, somewhat surprisingly, that there were problems with vehicles that are too heavy: "A downsizing of the heaviest light trucks could be a net positive."

He said the country would be better served by less diversity in vehicles, in terms of weight and size. In effect, he is playing to both sides of the debate, arguing that bigger is better — but that too big is not better.

Now he faces the difficult task of selling his ideas.

"The curious thing about the administration's effort on this proposal is that it is opposed by all of the major stakeholders, by the U.A.W., the environmental groups and by the major automakers," said Alan V. Reuther, the top lobbyist of the United Automobile Workers union.

The union fears that domestic automakers will abandon production of smaller cars under a Bush plan and focus on their profit center: sport utility vehicles and pickups.

Automakers expressed a range of views, but always concern.

"What the auto industry and other industries support about Dr. Graham is that he does strive to base decisions on sound data and sound science, and that's a mantra of business," said Gloria Bergquist, spokeswoman for the Alliance of Automobile Manufacturers, the industry's main lobbying group.

"But when he's starting to take on changes to CAFE, it makes us nervous because it's very complicated and it's something that we've wrestled with for 30 years."

The notion of Dr. Graham's presiding over the debate is anathema to environmentalists, who doubt that conserving gasoline will be a priority, and safety groups, who do not trust him because the Harvard Center for Risk Analysis, which he founded, was partly financed by automakers.

"It's clear he's doing this on behalf of the auto industry," said Joan Claybrook, president of Public Citizen, a consumer advocacy group and a critic of Dr. Graham.

She said the effort should be led by the agency she once ran, the National Highway Traffic Safety Administration. "That's why they create these agencies," she said.

Dr. Runge, the traffic agency's current administrator, has a leading role because his agency actually writes the regulations, though Dr. Graham has used his power in the budget office before to reject a tire pressure regulation proposed by the traffic agency.

The two men seem closer to the same page on the weight debate. Dr. Runge called Dr. Graham "a very valuable player in helping the administration navigate through this thorny issue."

"This is very important to the future of the country," he added. "It may seem arcane outside of Washington, D.C., but it affects everybody in our nation."

Fuel regulations are so strewn with loopholes that several auto lobbyists said they preferred "the devil we know."

Today, each automaker's fleet of passenger cars is required to average 27.5 miles per gallon. Light trucks are required to average 20.7 miles per gallon. The Bush administration has already raised that figure, to 22.2 by the 2007 model year.

But the system allows automakers to assume their vehicles are about 18 percent more fuel-efficient than they actually are. They also get special credits for making some vehicles that can substitute ethanol for gas even though few customers realize they have such an ability.

The largest sport utilities and pickups, those with a weight greater than three tons, are not even part of the regulatory system. That means automakers do not have to count many Hummers, Toyota Land Cruisers or Lincoln Navigators, to name a few.

Perhaps the ultimate quirk is that regulations meant to save gasoline led the auto industry to dump the station wagon, because it qualifies as a car, and create new classes of family haulers, like sport utilities, that qualify as light trucks. As a result, the fuel economy of the average new passenger vehicle is at its lowest point in 22 years.

But many automakers and their allies have long argued, and continue to argue, that saving gasoline kills.

Tough regulations would "exchange body bags for oil barrels," Jerry Curry, the top auto regulator during the first Bush administration, said in 1990. In 1999, Michigan's senators, Carl Levin and Spencer Abraham — Mr. Abraham is now the energy secretary — wrote to colleagues that higher CAFE standards would equal more vehicle deaths because cars would be made too light.

Last year, to ward off another attempt to raise fuel standards, the industry ran advertisements suggesting farmers would be forced to haul hay with subcompacts and warning: "Fuel economy is important. Safety is vital." Trent Lott held up a picture of a tiny European Smart car on the Senate floor — it was purple — to warn that Americans would be forced to drive such Lilliputians.

Sam Kazman, general counsel for the Competitive Enterprise Institute, which has sued the government to halt even small regulatory increases, said in a recent statement that fuel regulation "kills thousands of people each year by forcing vehicles to be downsized and therefore less crashworthy."

But Clarence M. Ditlow, director of the Center for Auto Safety, said Mr. Kazman "has no argument on small cars because the small cars have gotten bigger."

"When you look at today's fleet, manufacturers have not met the regulations by making small cars," he added, but by improving technology.

Mr. Ditlow argues that safety problems could be alleviated — and gasoline saved — if the separate standard for light trucks were scrapped. But the industry has blocked several efforts to do so.

On average, cars have been gaining weight for a decade and a half, to 3,408 pounds today from 3,013 pounds in 1987. Some additional weight has come from new safety systems like air bags. Car weights have consolidated at 3,000 to 4,000 pounds — a trend that on its own would help safety because cars are more alike in terms of weight than they were 30 years ago.

If the lightest cars have vanished, so have the behemoths of Motor City's last heyday — the two-and-a-half-ton Lincolns and the battleship station wagons. Even after bulking up in recent years, passenger cars are below the 4,071-pound average of 1975.

Large cars have been supplanted by light trucks, which have grown to more than half of sales today from a fifth in 1980. Sport utilities and pickups are gaining faster than cars, to 4,569 pounds today from a low of 3,840 in 1987, increasing the weight disparity on the roads.

The industry's arguments were bolstered by a 2001 National Academy of Sciences report, which said that cars being made too light caused 1,300 to 2,600 deaths in 1993.

But the finding drew dissent from two of the academy's panelists, and Charles Lave, an economics professor at the University of California at Irvine who was a primary architect of the finding, said much had changed since 1993.

"It's a description of the past," he said. "You can get a 20 to 40 percent improvement in fuel economy without decreasing weight. You don't have to decrease performance either. The technology exists to do it."

"There's no reason you should get an increase of deaths," he added.

The administration is likely to submit several ideas for public comment this summer, mostly variations on a system that would mandate light truck fuel efficiency in terms of weight or size classes instead of a single mileage target, several people who ae close to the deliberations said.

Environmental groups say such a system will nullify fuel economy gains. The administration, however, is considering bringing Hummers and Land Cruisers into the regulatory system and effectively creating a heavyweight class like one suggested in the National Academy's report, with a somewhat demanding mileage target to stem further auto obesity.

"My intention is to seek wide public comment on this topic to the point of public meetings," Dr. Runge said.

ETROIT, Aug. 11 — General Motors and DaimlerChrysler are dropping lawsuits against California over a landmark clean-air regulation that requires the production of millions of low-emission cars and trucks over the next decade and a half.

The move creates a temporary but momentous environmental truce between the auto industry, which has blocked the zero-emission vehicle mandate that was set in motion in 1990, and California, which wields enormous influence over the global industry.

The threat of the Z.E.V. mandate, as it is known in the trade, spurred the development of hybrid vehicles, which supplement gasoline with electric power. Now, with the dropping of the legal challenge — unless other hurdles emerge — every major automaker will have to start selling a range of vehicles with low emission levels of smog-forming pollutants, like hybrids and specially modified gas cars, in a plan that will phase in such vehicles in California between 2005 and 2020.

Automakers will also have to sell tens of thousands of zero-emission vehicles, either battery-powered cars or, far more likely in the long term, vehicles powered by hydrogen fuel cells.

"Given the fact that General Motors and DaimlerChrysler, the companies with most concern about the regulation, have come to agreement," said Dr. Alan C. Lloyd, the chairman of the California Air Resources Board, "I'm hoping it spells a new era of working more effectively together."

G.M. — which sells some high-emission vehicles like Hummers, Cadillac Escalades and Chevrolet Suburbans — withdrew from the battle as part of an effort to enhance its environmental image that included a previous announcement that it would sell hybrids.

But it has also been reassured by recent steps of California regulators. The state amended its requirements in April to emphasize more low-emission and fewer zero-emission cars. In recent weeks, coinciding with negotiations over the suits, the air board expanded its credit system for hybrids to include a wider variety of vehicles.

Elizabeth Lowery, G.M.'s vice president for the environment and energy, said: "One thing we've been working hard on is getting credit for all the things we do, but people are focusing on the litigation in California. We think we have enough flexibility in this rule in order for us to put this litigation behind us."

A spokeswoman for DaimlerChrysler, Ann Smith, said "we've had constructive discussions regarding the settlement" but declined to elaborate. The two big auto companies had filed their lawsuits jointly, but no other major manufacturer took part.

The industry and the state could soon clash again. Last year, California passed the nation's first legislation aimed at limiting automotive emissions of greenhouse gases, and a legal challenge is seen as a strong possibility.

Dr. Lloyd said the greenhouse-gas law was pointedly not a topic of debate while the two sides were negotiating. "We stayed very much away from that," he said, adding, "It's our hope that we will be able to work together on the greenhouse-gas regulation."

Ms. Lowery of G.M. said: "We don't think mandates are a good idea. The resolution of this does not change that position." She added that "the industry will challenge any regulation that is pre-empted by federal law."

The zero-emissions mandate was challenged in court on the ground that parts of it went beyond matters of vehicle emissions and tried to supersede federal authority to set fuel economy standards; a Bush administration filing supported the suit.

The industry could have a stronger case on greenhouse-gas emissions, because they are directly correlated to fuel economy. Emissions of smog-forming pollutants can be filtered by catalytic converters.

California is the largest auto market, and is particularly influential because its air standards predated the federal Clean Air Act. The state thus sets it own air standards and other states can choose California's tougher rules over federal regulations. Northeastern states that have followed California on air-quality standards, like New York and Massachusetts, have previously announced plans to adopt their own versions of the zero-emissions regulation. That will mean that advanced-technology vehicles will be more widely available there.

The zero-emissions mandate was introduced in the early 1990's, intended to spur development of battery-powered cars, which the industry now sees as a dead end. Many automakers, though, have built up credits by selling a variety of such vehicles, from gussied-up golf carts to an electric version of Toyota's RAV4 sport utility.

The current zero-emissions rule is focused more squarely in the long term on fuel-cell cars, which are electric cars with an onboard power system that generates electricity through a chemical reaction involving hydrogen. Fuel-cell cars emit only water vapor, though producing hydrogen leads to varying emissions.

The Bush administration has also talked up the promise of hydrogen, even in the State of the Union address, but has so far restricted its activity to financing research.

Automakers are also working on more immediate technologies to cut emissions, from hybrids to advanced diesels to improved internal combustion engines, and any one of them could play a role in meeting the zero-emissions mandate.

"Basically, we're talking about a giant technological horse race here and everyone's hoping their horse is Seabiscuit," Gary Cowger, G.M. president of North American operations, said last week.

He added that G.M., like other automakers, was hedging bets by developing a variety of prototypes. The settlement coincides with G.M.'s demonstration of many of its green vehicles at Dodger Stadium this week. Earlier this year, it announced a plan to start selling hybrid vehicles of various types, the most ambitious being a hybrid version of its Saturn Vue sport utility in 2005. Toyota and Honda already sell hybrids. G.M. has also been bullish on the fuel cell.

Environmental advocates said the prospect that the zero-emissions mandate would take effect after so many years of regulatory limbo would keep California well ahead of the federal government. Their frustration with Washington and Detroit has grown along with sport utility sales. In the 2002 model year, the fuel economy of the average new American passenger vehicle reached a 22-year low.

"The Bush administration has been talking about a fuel-cell vision; California is actually delivering on one," said Jason Mark, director of the clean-vehicles program at the Union of Concerned Scientists.

"It's encouraging that G.M. has decided to join the fight for clean air in the state," he added.

Such groups remain wary of G.M., however. "By suing California on environmental laws and building Hummers, they seem like they're in a race to the bottom to be seen as the worst environmental auto company," said Roland Hwang, a senior policy analyst at the Natural Resources Defense Council.

Dropping the suit "removes a real black eye for the company," he added, "but that's a far different thing from saying it will enhance their image."

In California, other factors could influence the regulatory landscape, like the gubernatorial recall campaign. It features Arnold Schwarzenegger, the biggest celebrity booster of G.M.'s Hummer, and the columnist Arianna Huffington, an outspoken basher of sport utilities who has likened the current campaign to "the hybrid versus the Hummer."

A new governor would have the power to replace Mr. Lloyd.

Mr. Schwarzenegger, though, may have an affinity for fuel-cell-boosting regulation. In "Terminator 3," his friendly cyborg character informs the audience that he is powered by hydrogen fuel cells. Unfortunately, the cells have a tendency to rupture and explode, like everything else in the movie.

Dave Barthmuss, a G.M. spokesman asked for comment, replied, "Those aren't G.M.-designed."

ETROIT, Sept. 9 — A task force of auto industry engineers has proposed redesigning some sport utility vehicles and pickup trucks so they inflict less damage on cars and making side air bags standard equipment on all vehicles.

The proposed standards, aimed for the end of the decade, are part of a broader industry effort to improve the safety of sport utilities and pickup trucks.

Automakers have yet to sign off on the proposals, which were sent to them a couple of weeks ago. The plan was reported today by USA Today.

"There is a technical agreement, not a commitment yet," said Brian O'Neill, president of the Insurance Institute for Highway Safety, a research group financed by auto insurers that has taken a leading role in the effort to develop the standards.

"The working groups have come to agreement. The question now is, Will the manufacturers sign on? We believe they will."

Eron Shosteck, a spokesman for the Alliance of Automobile Manufacturers, would not comment on the process beyond saying, "It's a work in progress and we expect to have it completed by the end of the year."

The alliance is the chief Washington lobbying arm of the major automakers, with the exception of Honda.

Edward B. Cohen, a spokesman for Honda, said "we support the effort," adding, "We think this is a very positive development."

General Motors, the world's largest automaker by volume, supports the recommendations of the task force, according to someone close to the company's deliberations. G.M. officials declined to comment on the issue, as did officials at the Ford Motor Company.

Associated Press The bumper of a sport utility vehicle looms over the bumper of a smaller sedan, a difference that can be significant during an accident.

The booming sales of light trucks — sport utility vehicles, pickups and minivans — have put people in passenger cars at an increasing safety disadvantage on American roads, federal regulators have said. At the same time, people in sport utility vehicles and pickups have not reduced the threats to themselves, because their vehicles are more prone to roll over than passenger cars, according to crash statistics. Both the Bush administration and Congress have pressed the industry to address such trends. In February, the industry announced that it would work jointly on the problem in conjunction with the insurer's safety group. The effort followed prodding by Dr. Jeffrey W. Runge, the Bush administration's top auto regulator and the head of the National Highway Traffic Safety Administration.

Dr. Runge has indicated that he would be satisfied by a self-regulatory approach, but Senator John McCain, the Arizona Republican who is chairman of the Commerce Committee, has expressed skepticism and countered with his own proposals.

The task force formed as part of the voluntary effort was divided into two working groups composed of auto engineers and experts from safety agencies in Britain and Canada. One group studied how to improve safety in head-on collisions. Another addressed side impact, a particularly difficult issue because there is relatively little space to buffer people in vehicles.

The national traffic safety agency was left out of the process because of regulatory complications that would have arisen from its involvement, including making the process public.

"They couldn't have participated as an active member because of all the rule-making restrictions," Mr. O'Neill said.

The working groups are proposing a set of crash tests that will effectively require side air bags with head protection systems for the vehicle to pass. A recent study by the insurance industry indicated that side air bags with head protection could reduce the risk of dying in side-impact collisions by half. But side air bags will be standard in only about 27 percent of 2004 model vehicles, and many are designed to protect only the chest.

A second proposal would require automakers to design sport utility vehicles and pickups so that the parts of their front ends that absorb crash energy, like the bumpers and steel rails of the frame, overlap with at least half of the same area of passenger cars. Alternatively, light trucks could be outfitted with "blocker beams," which are steel bars below the bumper that engage the front end of cars in an attempt to prevent them from being plowed over.

The new standards are expected to be phased in starting in 2007, or the 2008 model year, and be standard for all vehicles by 2009, or the 2010 model year, according to people close to the planning.

Joan Claybrook, president of Public Citizen, a consumer advocacy group, said, "I think the auto industry is trying to head off both regulation and legislation, but their proposal is very deficient because there is no requirement that they do this, and some companies might change their mind."

Proposals laid out in June by the Senate Commerce Committee, as part of a federal highway financing bill, would additionally include regulations aimed at preventing rollovers and injury once rollovers occur.