Inventor Dean Kamen admits that the Segway can never completely replace the car, because it doesn't have near the same capabilities. The standard HTi80 model only goes about 12 miles per hour (20 kph), and it has to be hooked up to household electrical current for about six hours to store up enough juice for a 15-mile (24-km) journey. Obviously, this sort of machine wouldn't do you much good on a cross-country road trip.

But Kamen does believe the Segway is a superior option for getting around a city. Cars take up a lot of room, so as soon as you have a bunch of people driving in a constrained area (like a city street), you get heavy traffic jams. It's also a hassle to park cars, and they are very expensive to maintain. All in all, a car is not an optimal machine for short trips in a crowded area.

Photo courtesy U.S. Patent and Trademark Office
Several alternative Segway designs from one of Dean Kamen's patent applications

The Segway is only slightly larger than a person, so it does not cause as much congestion as a car. As a sidewalk vehicle, it lets commuters zip through crowds, skipping the roadways completely. Just like scooters and bicycles, the vehicles will be involved in a good number of pedestrian accidents year to year. But the Segway's supporters say it's only about as dangerous as walking, since the vehicle moves at relatively slow speeds.

While it can't get people to their destinations at top speeds, the Segway can zip by slow-moving, bumper-to-bumper traffic. Once they get to their destination, riders can carry their Segways inside with them without worrying about parking. And there's no need to stop by the gas station, as the vehicle runs on ordinary household electricity.

Segways are also good machines for getting around crowded warehouses, where tight corridors make it difficult to use bulkier vehicles. People may find them useful for getting around large pedestrian areas, such as airports or amusement parks. There is really no limit to how people might use the vehicle. The Segway can fit in most places you might walk, but it will get you there faster, and you won't exert much energy.

So far, the Segway hasn't made a whole lot of progress changing the world. Since 2002, sales have only numbered in the tens of thousands. The hefty price tag has probably been an obstacle. However, the company recently announced that it will offer financing and leasing options. Segway also hopes that rising gas prices will help to boost sales.

Kamen believes more and more people will want the machine, after they get familiar with it and see what it is capable of. To this end, he initially targeted government agencies and large corporations, not the consumer market. Three groups in Atlanta, Georgia, including the Atlanta Police Department, were the first to try out the Segway on city streets. Currently several police forces, including the Chicago Police Department, use the HT i180 Police model.

The Centaur Only three years after its first mobile wonder, the folks at Segway focused on a four-wheeled, sportier sibling for the original Segway -- currently named the Centaur.

Definitely sharing very similar lineage (the main gyroscope-balanced base), the new kid on the Segway block is equipped with more than two extra wheels. The steering utilizes both drive-by-wire technology and regular steering mechanics. While the four-wheel design gives it added maneuverability and a little more speed, drivers can switch up between using all four wheels or just two.

Think of it like having an SUV: For street driving, there's no need to turn on the four-wheel-drive system in your Touareg; but when you want to take it off-road, the capability is there. Centaur is an SUV, too -- a "Segway" utility vehicle, able to cover more ground, literally, than its older sib.

For now, the Centaur is merely a prototype in development.