The debut of the Segway Human Transporter in 2001 surely set the bar for anticipatory hype. Remember "Ginger"? Or was the code name "IT"? But sales of the "revolutionary," self-balancing two-wheeler never approached those of a truly paradigm-changing innovation, such as Apple's iPod. Even five years after the Segway's much ballyhooed introduction, fewer than 24,000 of them cruise the world's sidewalks, pathways, pedestrian malls, and (local laws permitting) bicycle lanes and streets. Still, engineer Dean Kamen's novel electric scooter has managed to attract a lively cult following.

Recently the Bedford, N.H., company rolled out its second-generation Segway Personal Transporter (PT), which comes in an urban/suburban model called the i2 and a beefier, wide-track cross-country version, the x2. The time seemed right to give this intriguing technology another look and perhaps to clarify its place in a wheeled-transportation spectrum dominated by cars, motorcycles, scooters, motorized carts and bicycles. I talked to Segway users, dealers and designers, then briefly drove the i2 and x2 myself.

"Just step up like it's a stepladder," Ed Tsang urges, having just finished sweeping a clear path among the windblown autumn leaves strewn across the parking lot of his Segway dealership in Basking Ridge, N.J. I am mounting what vaguely resembles a modernized version of an old push-type lawn mower, except with a low-slung footpad in place of the rotating scythe blades. Further inspection confirms that the PT is more slickly designed than the original model, but the layout looks similar. I grab the T-shaped handlebar, step onto the platform very gingerly (almost as if it could somehow cut my foot) and finally board the vehicle. As if from a distance, Tsang's well-worn teaching litany just manages to penetrate my consciousness: "Relax ... Don't look down; look forward ... Stand up straight with your knees bent ... Try not to rock back and forth ..."

You are sure to start your first Segway ride a bit jumpy and unsure, seemingly primed to tip over. But after shifting about a little, you realize that all you really need do is "trust the machine," as Tsang advises. Make that leap of faith, and the gyro-stabilized device's intuitive control system does the rest, allowing you to direct it nearly effortlessly. So I stand tall and lean my body forward, and the i2 powers ahead smoothly and silently at walking speed. No doubt about it, a few moments gliding about on the uncannily responsive Segway shows that it is great fun, confirming the dealer's comment that "the Segway always exceeds initial expectations."

The trick to the Segway's uniquely satisfying ride experience is its user interface, says Doug Field, the company's chief technology officer. As in the original version, the automated control's nearly instantaneous sensory feedback mechanism relies on two safety-redundant microprocessor-based controller boards, five micromachined gyros, and a pair of tilt-sensing accelerometers that check the two-wheeler's condition 100 times a second. Then it deftly maintains balance by directing the electric motors to rotate the wheels just enough to keep the machine directly below the user's center of gravity. When you pitch forward slightly, you upset the balance, and the Segway rolls ahead a tad to keep you from falling over. Angle back some, and the machine compensates at once. Soon, standing in place is no chore at all. Tilting back a bit (even by extending your rear end a little) while traveling forward immediately brings the device to a smooth stop via a regenerative braking system that stores wheel-rotation energy in the battery.

To develop the machine's distinctive operation, Field says, Segway designers drew lessons from the familiar act of walking. Human environments are built around the assumption that people are standing and walking, he explains, adding that "walking is actually a form of controlled falling." During each step, your brain senses you are out of balance, because fluid in your inner ear shifts, so it triggers you to put your leg forward and stop the fall. Engineers conceived the Segway "as a way to graft wheels, motors and batteries onto a person so as to amplify walking in a way that mirrors walking, which is suited to our environment." [break]

The new steering controls on the PT take this concept one step further. To turn the earlier model, the user had to rotate the left handgrip on the T-bar forward or rearward, like a motorcycle throttle. Although the skill is easy to learn, Segway engineers improved on this scheme by installing a "lean-steer" mechanism that allows users to corner by leaning into turns (shifting their weight in a slalomlike fashion) while tilting the handlebar--a much more natural motion. Push the bar all the way over, and the Segway rotates sharply in place, as one wheel advances while the other reverses.

The PT's new, larger lithium-ion battery pack (located under the footpad) can power both Segway models to a maximum speed of 12.5 miles an hour, the same as the initial versions. The i2 goes 16 to 24 miles on a charge, whereas the x2's range is 10 to 12 miles (comparable to that of previous models). Another useful upgrade is a wireless infokey fob that provides a readout for speed and distance traveled and enables a user to start a Segway remotely, control its top speed and rapidly engage the lock/security system.

As with most novel technologies, the Segway has faced a bumpy road. Service as a golf cart might seem like a surefire application, for example. But the two-wheelers have failed to prosper on the links because few golfers know how to use them, whereas anybody can drive a golf cart.

Current users come in three categories, says Barry Fulton, owner of Segway of Long Beach in California. The urban commuter wants to ride the short distance from home to work and back in business dress without having to drive and park a car. The recreational user just likes gliding around for fun or to do chores. This person is typically "a 55- to 75-year-old male with money who wants to let the kids play with it or ride it off his docked yacht." This category also encompasses some travel tourists, who, for instance, can rent a Segway from Fulton to explore the Long Beach shoreline and the HMS Queen Mary for $99 a day.

The third category comprises "commercial" customers, including police departments, security firms, warehouses and companies with large campuses. One of Fulton's clients uses Segways to replenish 85 delivery trucks, parked across a seven-acre plot of land, with vending-machine supplies. In the Midwest, another corporate customer is the security patrol for a large telecommunications firm that operates a 235-acre complex. Rather than walking beats, the crew Segways around the grounds. With Segways, the security chief has been able to shrink his staff, because each member can cover a greater area, and the vehicles have also lengthened the careers of older workers, who were finding the constant walking increasingly difficult. The chief says that the machine's elevated driving position is helpful for handling crowds--each agent sees the surroundings better and is more visible to bystanders.

Despite the improved technology and growing public familiarity, the Segway remains a niche product. Why the resistance? The consensus among sellers and users alike comes down to sticker shock. At $4,000 to $5,500 apiece (a significant fraction of which pays for the batteries), the Segway is simply too pricey for those without a compelling need or use for it. As one observer notes, "Most potential buyers consider it as a fractional car, and at $5K, it just doesn't supply enough utility." Cut that price in half, and sales will spike, dealers claim, but there is little prospect that battery costs will drop precipitously anytime soon.

Gliding around on a Segway is a delight, but you have to wonder whether the technology is a solution chasing a problem. Still, it took a while for the Frisbee to catch on, but the unusual flying disk eventually found its place in the market. Maybe it's only a matter of time until the same thing happens to the Segway.