The high-tech, two-wheeled, electric human transporter known as the Segway can cruise on the waterfront but not on the hilly sidewalks of San Francisco. In Florida, legislators think they're all right, if kids who ride them wear helmets. Nebraskans like them, except on freeways. And in Washington, D.C., they can go just about anywhere, except the Mall.

And maybe not always on Metro, but no one's sure of that yet.

Across the country, officials are scratching their heads, trying to figure out what to make -- legislatively -- of this new technology, a device that glides ahead with a gentle lean forward, to a top speed of 12.5 mph, and stops on a dime with the plant of a heel. Should it be treated like a bicycle? A motorcycle? A pedestrian?

Particular attention is being paid to the way Washington handles this. Not only is the nation's capital seen as the ideal Segway city, because of its open spaces and sidewalks with ample ramps, but it is also host to the national Segway convention this fall.

"Nationally, a lot of people are looking to see what we're going to do," said Metro Transit Police Chief Polly Hanson, who made clear her distaste for Segways at a recent meeting during which she urged that the transit system impose a rush-hour ban on them.

As silent herds of tourists mounted on the machines glide through popular vacation spots and handfuls of commuters float past walkers, city and state lawmakers are stitching together a patchwork of laws and codes without knowing quite what they're dealing with.

"It really is an emerging technology, and there's no federal code or law that talks about Segways," said Alexa Viets, the National Park Service's transportation manager for the Mall, where Segways have been banned pending further review. "A lot of people are trying to figure it out."

Meanwhile, enthusiasts are anxiously tracking the decisions on their Web sites -- plotting state regulations on color-coded maps to highlight Segway-friendly places -- and lobbying in places where lawmakers are flummoxed by or hostile to Segways.

In the District, about 120 Segway owners chat online and get together for group glides. "We're not really a lobbying group. Really, we got together for fun, as an owner-enthusiast group," said one of the group's founders, William W. Hopper, who recently took part in a U.S. Department of Transportation study of the device, navigating an obstacle course for a team of analysts. "But it looks like we may have to start doing some advocacy work now."

The devices, which sell for about $4,500, didn't seem to faze national park officials a couple of years ago, when the occasional machine garnered nearly as much wonderment as the monuments. There were no complaints, no injuries and no reason to do anything about them.

Tim Kanaley was one of those early riders, a consultant who got rid of his car after finding the three-mile commute from his Logan Circle NW home to his Southwest office cheaper and more fun by Segway.

But when a local tour group approached the Park Service about allowing up to 20 Segways on the Mall for twice-daily tours, park officials hesitated, Viets said.

The officials barred them from the Mall and memorial grounds. They will reconsider the prohibition as part of wider transportation study this fall.

Until the Park Service decides on a policy, Segway riders are allowed to cross the Mall only along streets owned by the District -- Third, Fourth, Seventh and 14th streets, Viets said.

"The rules they're making are really catch-as-catch-can," Kanaley said.

City Segways Tours has a map for guides showing the circuitous route they're supposed to take, said D.C. tour manager Brian McNeill.

From Paris to New Orleans, the group has stumped some city council each time it has introduced its popular tours. The mishmash of rules reflects the confusion.

"It really varies. Right now in D.C., the age limit is 16. But in every other city, it's 12. In San Francisco, we can only go on the waterfront. We had a really hard time in New Orleans," McNeill said.

In New Orleans, tour operators haggled for months with city officials about where the machines could travel, he said.

In many cases, city officials worry that Segways are unsafe. President Bush famously fell off one that he mounted before its balancing mechanism was turned on. But McNeill said the D.C. group has had to call 911 only three times since tours began last year.

"Once, a guy fell and scraped his elbow a little, then passed out when he saw the blood," McNeill said. The other accidents were minor scrapes involving riders who weren't paying attention and bumped into other riders. "The injuries weren't as bad as something you'd get riding a bike," McNeill said.

"It's a whole different world of physics and isn't anything like a bicycle," said Chris Walker, a Utah Segway rider who is one of the founders of SegAmerica, a national group. He has testified before a borough council in New York and advised a rancher in Montana, among other actions, in his quest for Segway-friendly legislation.

Walker compared the situation today to the early 20th century, when some cities banned motorcars, ordered drivers to light flares every mile to warn of their coming or even required that a motor vehicle be hidden if a horse-drawn cart was approaching.

At a meeting Thursday, Metro considered barring Segways from rush-hour trains and buses, but board members were split.

"I ride the system every day, and I haven't seen a problem," said Dan Tangherlini, the District's transportation director, who said that establishing regulations for the Segway is creating a solution for a problem that doesn't exist.

But Richard A. White, Metro's general manager, said a policy should be in place because he believes the system will soon be overrun.

Some thought Segways should be treated like bicycles or strollers or luggage.

Board member T. Dana Kauffman of Fairfax County moved to approve the rules, "before I get my toes crushed by one of these things."

That brought a swift response from Neil Schuldeinfrei, a Department of Energy lawyer who commutes on his Segway every day.

"If it ran over his toe, it would be less painful than if I stepped on his toe," Schuldeinfrei testified. "I hate that people make these assumptions about the Segway without being informed."

After much debate, the Metro board couldn't decide what to do and sent the issue back to the safety committee. "For more research, or something," said board member Jim Graham of the District, joining the state of confusion that the machines have created among policymakers.

Tourists such as sisters Sarah, left, and Laura Shinn can visit Washington sites by Segway.

Tour manager Brian McNeill, center, instructs customers Dusk Gray, left, and Margaret Rivera on operating a Segway.