Like many of her neighbors, Maria Recchia-O'Neill has a sport utility vehicle sitting in her driveway in Rye Brook, just north of New York City. She drives it to work and around town to run errands. But although her vehicle looks like any other SUV, her Chevrolet Equinox gets excellent gas mileage—and it doesn't emit any pollutants or climate change–promoting carbon dioxide. That is because it is a hydrogen fuel cell electric vehicle—one of 40 such automobiles that U.S. carmaker General Motors provided for motorists to road test.

"My average right now is 44.4 miles [71.5 kilometers] per kilogram [of compressed hydrogen gas], which is supposed to be the equivalent of a gallon of gasoline," Recchia-O'Neill says. In only two weeks of driving, the district coordinator of science for the Port Chester, N.Y., public school system has driven at least 600 miles (965 kilometers) on the car and her fuel cell Equinox has gotten as much as 191 miles (307 kilometers) on its three full tanks (each holding slightly more than four kilograms, or 8.8 pounds, of compressed hydrogen gas). "I feel like I'm making history," she says. "It's an exhilarating ride because it's different."

Recchia-O'Neill is not the first American to drive a hydrogen vehicle, nor is her suburban family the first to enjoy it. That honor goes to the Spallino family of Redondo Beach, Calif., who got their Honda FCX sedan for test driving in 2005. Nor is the Chevrolet Equinox the first fuel cell vehicle General Motors (GM) has ever produced: The 1966 Electrovan, an unwieldy and prohibitively expensive fuel cell van that never made it out of the lab, was the first of about 40 or so hydrogen-fueled vehicles that have been built by the U.S. carmaker. She is not even the only one in Westchester County driving a GM fuel cell Equinox.

But Recchia-O'Neill is certainly at the forefront of a transformation of the U.S.—and global—auto market from standard gasoline-fueled internal combustion engines to greener vehicles. From so-called flexible fuel cars (that transition from ethanol to gasoline without a hitch) to gasoline–electric hybrids, new types of cars and trucks are finding their way onto the road.

Hydrogen fuel cell vehicles are vying with next-generation hybrid car technology (which can be plugged in to recharge its battery rather than relying on the gasoline engine) to be the electric car of the future. "We've got a real fun race going on here between plugging in vehicles and storing electricity in the battery versus pumping hydrogen into a tank and creating electricity from a fuel cell," says Larry Burns, GM's vice president of research and development. "We are going to need every Btu [British thermal unit] of energy that can be created from every pathway."

The Chevrolet Equinox starts with a chirping sound, as gas injectors pump hydrogen into its handmade fuel cell stack. Like all electric cars, acceleration is instant, uninterrupted—and silent. "The young guys ask, 'Can't this make some kind of growling sound?'" Recchia-O'Neill says of her son's college roommates. Even turning the car off is different. "The shutdown is the best part. Everybody likes to watch it purge with the water vapor coming out and a futuristic kind of sound."

The whoosh of compressors as the vehicle shuts down—a sound that Recchia-O'Neill says makes "you feel like you're in a spaceship"—is the key to driving it in frigid weather. Producing electricity in a hydrogen fuel cell has one by-product: water. And water can freeze at winter temperatures common in New York State. So GM has designed its Generation IV fuel cell assembly to eliminate all water from the stack when it stops operating. "It started up no problem in cold weather," Recchia-O'Neill says, even in a snowstorm and on days the temperature dropped below freezing.

Save for the quirky noises—or the lack thereof—the fuel cell light truck does not look or perform any differently than regular ones. The fuel cell version of the Equinox outweighs its standard cousin by more than 500 pounds (225 kilograms) thanks to its heavy nickel–metal hydride battery pack, GM says, but press down on the accelerator and the Equinox can run with the rest of the road traffic. "I will pass tractor–trailers," Recchia-O'Neill says. "I can dodge the taxicabs. It responds well. I feel like I'm a match for anyone on a busy road."

Honda, GM and other major carmakers, including BMW, Toyota, Ford and Daimler, are all currently testing model hydrogen cars and trucks. Recchia-O'Neill  became one of GM's hydrogen truck test drivers by accident when she visited the auto giant's Web site, which called for volunteers to participate in Project Driveway, an effort designed to have consumers put the Equinox through its paces. She is one of 11 "real customers" (as opposed to celebrities, politicians or the like) now taking the car for a trial run; GM plans to eventually have 100 such test vehicles on the road. As part of this effort, GM has also teamed with Virgin Atlantic airlines to provide pick-up and drop-off services in fuel cell cars to first class passengers at Los Angeles International Airport starting next month.

The U.S. Environmental Protection Agency has already certified hydrogen vehicles as zero-emission vehicles—they only produce water. And the U.S. National Institute of Standards and Technology has certified them safe to operate and refuel.

But two major roadblocks remain: The Equinox costs hundreds of thousands of dollars to make and it can be hard to find hydrogen fuel. The first will only be solved when companies begin to mass produce such vehicles, according to GM's Burns, which could happen as soon as 2012 when a law is set to take effect in California requiring that a portion of new cars emit no pollution. "It has one tenth the moving parts, and the geometry of an assembly line is easier than for an [internal combustion engine]," he adds. "This technology has low-cost potential."

As for the fuel, more than 45 million metric tons (45 billion kilograms) of the lightweight gas is produced every year as part of making fertilizer, chemicals and the gasoline used to power cars today. In fact, fully 25 percent of global hydrogen production is made by oil companies themselves at refineries to improve the quality of crude oil. "Why not just put the hydrogen in a fuel cell instead of putting it into petroleum? It's economical to do it at a refinery today," Burns says. The oil business makes enough hydrogen to fuel more than 30 million hydrogen vehicles, he notes, adding, "the petroleum industry will provide us with the hydrogen infrastructure." Already, GM has partnered with Dutch oil giant Shell to open hydrogen fueling stations.

Critics note, however, that hydrogen is simply an energy carrier—and not a particularly good one, effectively delivering less than 25 percent of the electricity required to produce it from water as energy to move wheels. Today's lithium ion batteries can return roughly 75 percent of the electricity put into them as motive force. Even GM's vice chairman of global product development, Bob Lutz, said recently that if energy storage in lithium ion batteries improves, it might not make sense to employ hydrogen instead of electricity directly.

But fuel cell advocates point out that given the space available in a car frame and the laws of thermodynamics, today's batteries can only provide a limited driving range—40 miles (65 kilometers) for GM's own Chevrolet Volt—before requiring a recharge, such as by the gasoline motor in a full hybrid like the Toyota Prius. Current hybrids without this feature already cost several thousand dollars more than their conventional counterparts and converting them to plug-ins would cost at least $10,000 more. The feasibility—and cost—of future plug-in hybrids will depend on advancements in battery technology.

Hydrogen production may also prove to be a better way of storing the energy from intermittent but renewable power sources, such as wind farm generation or solar photovoltaic panels on a future garage rooftop. Iceland and other countries are already testing such closed loop systems. And hydrogen can be produced from a wide array of processes, ranging from water electrolysis to the fermenting of biofuels like ethanol.

For now, Shell has two hydrogen refueling stations in the New York City area—one in Ardsley and the other newly opened in White Plains, both in Westchester County—and a third is planned at John F. Kennedy International Airport. The National Hydrogen Association counts 122 at present in the U.S. and Canada—most clustered around major cities, such as Los Angeles, San Francisco and Washington, D.C. The association estimates that an adequate hydrogen refueling infrastructure of 12,000 stations—less than one tenth of the roughly 170,000 gasoline stations in the U.S.—could be built for no more than $15 billion.

Recchia-O'Neill says she can pump enough compressed hydrogen into the Equinox's three carbon–fiber storage tanks in six minutes when the hydrogen gauge tells here she is "running on fumes—literally."

The next generation of GM's handmade fuel cell stack was showcased in the luxury crossover Cadillac Provoq at the Consumer Electronics Show in Las Vegas this past January. By doubling the power density of the fuel cell stack, GM engineers halved its size as well as halved the amount of expensive materials, such as platinum catalysts, that such fuel cells require. "That's the key to getting the cost reductions we're seeking," Burns says.

For now, Recchia-O'Neill will be one of the few to drive a prototype car of the future—and even she will only have it for three months total. But for those three months she'll need to set aside more time to go to the supermarket. "If I go grocery shopping, people stand around it," she says. "We go down the street and people look at you because they don't even know the car is running. … This is a real car for regular people, we're just waiting for the infrastructure to catch up."