An American inventor has at last unveiled an invention he claims will revolutionize transportation, much as the automobile did a century ago - a two-wheeled, battery-powered, single-person transporter that senses the rider's movements to determine direction and speed. The invention was shrouded in secrecy and heavily promoted before its unveiling.

For months, intense speculation focused on the mysterious invention known only as "IT," or its nickname, "Ginger."

"IT's" creator, Dean Kamen, finally put all the hype to rest when he unveiled what he called the "Segway Human Transporter" on Monday on the ABC network's morning television news program. "It's sort of like putting on a pair of magic sneakers," he said.

He said the Segway is an individual transport vehicle for what he called "empowered pedestrians."

It consists of a platform with two wheels, side-by-side. A rider stands on the platform and holds on to a handle-bar. Mr. Kamen says the Segway will not tip over, because it uses technology that replicates how human beings balance and walk. Mr. Kamen said, "It does what a human does. It has gyros and sensors that act like your inner ear. It has a computer that does what your brain does for you. It's got motors that do what your muscles do for you. It's got those tires that do what your feet do for you."

Sensors in the platform detect shifts in the rider's weight and tell the Segway to move forward, backward, turn or stop. Mr. Kamen says the vehicle transports riders at up to about 19 kilometers an hour.

And, in an era when the public is increasingly environmentally aware, Mr. Kamen says his invention will run for up to 27 kilometers per electric charge, and gives off no emissions.

Mr. Kamen is no ordinary inventor. His previous inventions include a portable dialysis machine, an insulin pump and a wheelchair that goes up stairs.

The U.S. Postal Service, the National Parks Service and the city of Atlanta are among the first customers waiting to try the transporter for their workers.

U.S. Postal Service spokeswoman Sue Brennan says the Postal Service will conduct a month-long test starting January 7. It will try out 20 Segway machines in three cities on the U.S. east coast - Tampa, Florida in the South; Concord, New Hampshire in the North and at the Postal Service's Washington, DC headquarters. She said, "The areas were chosen because of environment. We thought it was very important to conduct the tests in different regions that offered different route structures, different climates, weather conditions and different needs internally for manpower. With the sites we've chosen, we get warm and wet weather, cold and icy weather, and an inside environment and a multi-level building, which is our postal headquarters building.

Ms. Brennan says the U.S. Postal Service has been in talks with Segway for eight months. She said in tests, the vehicles have proven to be very balanced and very safe. "It is designed to go wherever a person can normally walk, over all types of terrain," she said. "And we do believe that this would be a benefit to our carriers. And another benefit is that, currently, the carriers that have walking routes, carry as much as [16 kilograms] of mail over their shoulder. And, with this vehicle, they would not have to do that."

The Segway Human Transporter will also be available to the general public next year, at a price of at least $3,000 each.