DETROIT (NYT) -- Trying to capture the spirit of the times, General Motors occasionally introduces a whole new brand, hoping it will grow as popular as Cadillac, Buick or Oldsmobile. A decade ago it brought out Saturns and Geos to tap a national desire for affordable, sporty, fuel-efficient cars.

Now GM is at it again. Its latest venture: the Hummer.

Like the Jeep but far bigger, the Hummer started as a military transport, the Humvee, which was used in the Persian Gulf war for everything from launching missiles to ferrying the wounded.

With the Cold War ended, the Humvee's manufacturer is looking to civilian buyers. It has sold about 1,000 a year, for about $100,000 apiece, to affluent entrepreneurs, limousine companies and a sprinkling of celebrities like Arnold Schwarzenegger, Mike Tyson and the rapper Coolio.

GM recently acquired the Hummer brand, placing a big bet that the decade-long trend toward ever larger and more aggressive-looking sport utility vehicles would continue. Besides selling the current version, GM will introduce at least two smaller Hummer models over the next three years, at much lower prices than the current model.

With a national network of Hummer dealerships, and plans to pursue the New York market in particular, the company expects to make Hummers as common as BMWs, with sales approaching 150,000 a year.

"You'll see a lot in New York City, places like Manhattan where your affluent buyers are," said Michael DiGiovanni, GM's general manager of Hummer operations.

But the mass marketing of Hummers raises the same safety and environmental issues that have dogged the largest sport utility vehicles: extremely poor fuel efficiency, higher emissions of smog- causing pollutants than cars, and a variety of risks and annoyances to motorists in other vehicles.

Even without its military look or a celebrity at the wheel, the Hummer would be hard to miss: It is taller, much wider and a full ton heavier than even GM's largest sport utility vehicle, the Suburban. Indeed, while it seats only four, the current Hummer weighs as much as two Jeep Grand Cherokees or three small cars.

GM says its research shows that many prosperous baby boomers cannot afford the current model but still love its military look. GM's surveys have found that the Hummer is also the favorite brand of teen-age boys and the third favorite of teen-age girls, after only Volkswagen and Saturn. That is especially important to GM because people tend to form lifelong preferences during their teens.

The Hummer's teen-age admirers include Cooper Schwartz of Bellevue, Wash. As a small boy, he used to collect model sports cars - - Corvettes, Porsches and Ferraris. Now 17, he keeps a scale model of a black Hummer on the shelf next to his bed, and dreams of the day when he can afford a real Hummer.

"I love the fact that the Hummer is a tank; it's like a tank with fashion, it's like having your own war toy," said Schwartz, co- captain of his high school football team. "I like something where I can look down into another car and give that knowing smile that `I'm bigger than you.' It makes me feel powerful."

Indeed, the Hummer can seem downright overpowering compared with other passenger vehicles, raising the issue of safety.

The current Hummer has 16 inches of ground clearance, half a foot more than any other mass-market sport utility, and is designed to climb over vertical walls up to 22 inches tall.

Federal regulations require car bumpers to be 16 to 20 inches high. So the Hummer's height greatly increases the risk in crashes that the vehicle will ride over cars' bumpers and door sills and slam into the passenger compartment. And because the Hummer is so heavy, it inflicts far more damage in crashes.

While future Hummer models will have somewhat less ground clearance and weigh somewhat less, they are being designed with a central goal of "unparalleled off-road performance." So they will still be tall and heavy enough to pose problems for safety engineers like Terry Connolly, GM's director of North American vehicle safety, who said that his office had played little part in the company's Hummer planning and design.

Even more than other sport utilities, Hummers can block the view of other motorists. While cars tend to be 5 or 6 feet wide, and most sport utilities are a little over 6 feet wide, the current Hummer is 7 feet 2 inches wide, and GM's prototype for a model the length of the Chevrolet Tahoe full-sized sport utility is 6 feet 10 inches wide.

GM says that the unusual width of Hummers is part of their brand identity, so that even the smaller Hummers will be extra wide, making them hard to park as well. The wide stance should reduce the risk of their rolling over, however.

Among the environmental problems, the Hummers will emit far more air pollutants than cars. Current federal rules allow large sport utilities to emit 5.5 times the smog-causing nitrogen oxides that cars do. While Ford has improved its sport utilities and pickups so they pollute no more than cars, GM does not plan to reduce air pollution from its Hummers and other large sport utility vehicles until required to do so by federal regulations in 2004.

Fuel economy is another issue. AM General, the military contractor that developed the vehicle, says that the current Hummer gets 13 miles to the gallon in the city and 15 on the highway. The Hummer manages this mileage only because it has weak acceleration and burns diesel fuel, which gives 35 percent better mileage than gasoline.

GM plans to make its next Hummer, like the current one, heavy enough to be classified as a medium-duty truck and therefore exempt from federal fuel-economy rules.

But Harry Pearce, GM's vice chairman, said GM would include Hummers in its voluntary commitment, announced on Wednesday, to have better gas mileage than Ford for sport utilities in 2005. GM will have to make its other sport utilities much more efficient to offset the Hummers.

The Hummer as a passenger vehicle also troubles some U.S. war veterans. Hummer buyers typically have not served in the military, let alone fought in combat. "It's like someone who always wanted to be a cowboy and who goes out later in life and buys a hat and a horse -- well, that doesn't make you a cowboy," said Bruce Harder, a retired Marine colonel who is now director of national security and foreign affairs at Veterans of Foreign Wars.

During the Reagan administration's military buildup, a large factory was built in South Bend, Ind., to manufacture 25,000 Humvee military transports a year. Production soon plunged below 4,000 Humvees a year, so in late 1992 AM General began building nearly identical Hummers for civilians on the same assembly line. GM and AM General broke ground last Monday on a second Hummer assembly plant in Mishawaka, Ind.

GM will rely mostly on new models to increase Hummer sales, while continuing to sell the current Hummer, which it is renaming the Hummer H1. It plans to introduce in 2002 a $45,000 Hummer H2, to be built in Mishawaka, with maximum sales of 40,000 a year. The H2 will be the length of the Tahoe but considerably wider.

The Hummer H3, the size of midsize sport utilities like the Chevrolet Blazer or Ford Explorer, is to go on sale the following year for just under $25,000, as a higher-volume model aimed at a market of young men. GM has also done a little work on a possible Hummer H4, which would be slightly smaller and cheaper, but has made no decisions on it.

John G. Middlebrook, GM's vice president for North American vehicle brand marketing, said GM would choose some of its most successful dealers to sell Hummers. "Like when we started up Saturn, we have a clean sheet here," he said. Saturn sells 230,000 cars a year.

GM decided against a Hummer dealership in Manhattan because of real estate costs. Instead, it plans dealerships across northern New Jersey and Long Island, N.Y., and at least one for Westchester County, N.Y., and Fairfield County, Conn.

Paul Ballew, GM's general director for market analysis, said that the rising concentration of wealth and income in American society over the last two decades had been the single most important social trend for automakers. A very large class of high-income, fairly youthful households has been created, he said, and these people care little about gasoline prices and other expenses of operating a vehicle.

GM plans to aim the H1, H2 and H3 at different markets. The H1 will be marketed to "rugged individualists." These are people who are irreverent and daring and want to be seen that way by other people, DiGiovanni said. "The rugged individualists are people who really seek out peer approval -- they're really going to go off road, go out in the desert and come back and tell people about it," he said.