The voice in my head is telling me to do things. The commands are mostly benign and touristy:

"Turn left at the intersection."

"Look at that building on the right."

"Speed up. No, really, you have to catch up."

The disembodied voice barking orders from an earphone under my pith helmet sounds a lot like Brent Alexander, the tour guide at the head of a single-file line of Segway personal transportation devices gliding silently over the busy sidewalks of Downtown Pittsburgh.

If that sounds totally techy and 21st century, well, it is.

If balancing, steering and stopping the two-wheel contraption sounds totally difficult, well, it's not.

"If you can stand without falling over," says Alexander, "you can ride a Segway."

The patented technology, "dynamic stabilization," was originally developed to enable people in wheelchairs to go up and down stairs -- that personal mobility device being the iBot. The Segway, a spin-off product, premiered in 2003.

Bicycles and motorcycles are balanced by their operators, but Segways balance themselves. Complex interactions of five gyroscopes, two floor-mounted tilt sensors and a bank of microprocessors evaluate the operator's center of gravity 100 times per second. Step onto the platform between the two wheels and the Segway stands relatively still without tipping. Lean forward and it moves forward. Lean farther ahead and it goes faster. Lean back to slow to a stop. Newer models interpret leaning left and right as turning commands, but most of the Pittsburgh tour's Segways turn with a handlebar-mounted turning ring.

Don't count on a cardio-vascular workout -- a Segway ride is as invigorating as standing still, literally. But it's a fun way to get out, get some sun and see the city as you've never seen it before.

Segways were brought to Pittsburgh four years ago by guided tour entrepreneur Fred Anders. His independent company was imported from Florida, hence the name Segway in Paradise and the fake palm tree next to the registration desk tucked into a nook in the food court at the Freight House at Station Square.

Off the shelf, a new Segway retails for $5,300. Realizing it might take some time in the public eye before the revolutionary technology gains mainstream public acceptance, the company that invented it, New Hampshire-based Deka Research, is letting the world see the Segway by selling to independent tour operators such as Anders.

"The acceptance factor is much better in Pittsburgh than in any of the other cities we've been in," he says. "Usually, 80 percent of Segway tour business is from tourists, but in Pittsburgh over 80 percent of our business is from local people."

Segways are different from bikes and motorbikes in another notable way. The state of Pennsylvania classifies the Segway as an electronic mobility assistance device -- the same as a motorized wheelchair -- so it's not subject to the rules of the road. With a top speed of about 12 mph, driving on public streets is impractical, but driving on public sidewalks and even indoors and on elevators is OK.

Tour guide Alexander begins with a quick demo and a safety lesson inside Station Square. Shoppers stop, gawk and step out of the way as members of our small group practice getting on and off, moving forward and backward, turning and the all-important maneuver of stopping.

Reservations are recommended for Segway rides, but Gina and Randy Sporle, honeymooners from Janesville, Wis., see us zipping through the food court and hop onto the tour.

"We're looking for something fun and a little more interesting," said Gina Sporle.

Fitted with tan pith or bicycle helmets and wired to earphones, we trail off in a follow-the-leader line through Station Square. Alexander's voice cracks commands and shares details about the city as we navigate the sliding doors, cross the street and glide through Bessemer Court, over part of the Three Rivers Heritage Trail, across the Smithfield Bridge and into the city.

During training, the Segways' speed limit is preset at 3 mph. It's upped to 6 mph while gliding through the high-traffic Golden Triangle and 8 mph for the broad, open sidewalks of the North Shore.

At each intersection, we wait for a fresh light and glide across the street in line.

"Tighten up here. Close the line," says Alexander from the front. "Let's try to keep about three feet between the Segways -- no more, no less. I say that because if we're coming through an intersection and have more space than that, [motorists] who can turn right on red will drive between us. And on the sidewalks, if there's more space between us, pedestrians will step between our line."

The two-hour tour includes learning time, a rest break and a brisk 90-minute ride through the Cultural District and the North Shore. Alexander shares tour information that even locals may not know including the origins of KDKA radio, the City-County Building, the city's paved-over canal system, the U.S. Steel Tower, the "T," the stadiums and some of Pittsburgh's notable architecture.

In four years of Segway tours, he said, there was one significant rider mishap.

"The Segway you're on," he tells me, "was nicknamed Nemo, and the reason was it was in the Allegheny River."

A 15-year-old who didn't listen to his parents or the tour guides was hot-dogging on the North Shore and zigged when he should have zagged.

But Anders and Alexander say operator problems are rare on the Segway. The tour sets a minimum driver age of 10 and minimum weight of 60 pounds.

"I'm enjoying it," says Harry Miller, 71, of Greensburg. "I saw them on television; I always wanted to try one. ... When you get up in age, you don't have the balance that you used to have, but this does the balance for you, so it's no problem. Going forward and turning, that's easy. Standing perfectly still without drifting forward and back a little, that's Stage 2."

Miller's touring companion is his 14-year-old grandson, Travis Dominick of Hannastown.

"I want one," he said. "I like it."

Alexander stresses the green advantages of the zero-emission, electric power cell-driven Segway. Commercial applications seem strongest in the security sector. Alexander said several Pittsburgh shopping centers -- SouthSide Works, Pittsburgh Mills and Ross Park Mall -- have purchased Segways for their security personnel, and they're used by the military and some city police forces.

Segway in Paradise tours cost $25 plus tax for a 45-minute ride, or $59 plus tax for the two-hour tour. The honeymooning Sporles say the full ride is "definitely worth it."

"Oh, yeah," says Gina Sporle. "You're outside, getting fresh air, relaxing, you laugh a little, learn something about the city. It's not hard -- just turn slowly. Small movements go a long way."

Learn more about Segways at www.segway.com and www.segwayinparadise.com. For Pittsburgh Segway tours call 724-625-3521.