High-speed rail projects able to pick from several options.

Not all high-speed rail systems operate alike.

In fact, several technologies are being used for systems either being planned or already in use around the world. At this point, there are three primary approaches: electrical (New High-Speed Rail) and two versions of magnetic levitation (Maglev).

New HSR is the only high-speed system in use in the United States, as part of Amtrak's Acela line in the Northeast Corridor. But older lines that twist and turn have kept it from running at its maximum speed of close to 200 mph.

In California, the technology being considered for the L.A. area is the highly efficient Maglev, which would require an entirely new track infrastructure. The north-south line under consideration would use New HSR.

All three technologies were developed in the United States, but implementation has been hampered both here and "abroad by cost concerns. To date, only Shanghai has put a Maglev system to work, although it is being tested in Germany and Japan.

New HSR takes existing diesel-powered trains and converts them to electrical power.

They are powered by a current that is carried via wire cable running above the train and parallel to the track. Connecting poles at the top of each car pull power from the cable.

"The wire continues over the whole track and each train car has a connection to it. It runs through the car and runs the motors on the axle," said Robert McCown, director of the technology development program for high-speed rail at the Federal Railroad Administration, a unit of the U.S. Department of Transportation. "It effectively gives it access to unlimited power."

The connectors, which take the electrical current and transform it into a usable electrical charge, are among the heaviest parts of the train, though still it's much lighter than a diesel engine.

What's more, New HSR electric power is tapped from the existing power grid.

Upgrading existing infrastructure to use electrical power costs between $1 million and $9 million per mile. To reach maximum speeds, however, HSR requires an expensive investment in straight tracks. According to a 1997 report from the Federal Railroad Administration, laying New HSR tracks cost $10 million to $45 million per mile.

The speed advantage comes because these trains are lighter than diesel-powered locomotives, which were designed for strength and dig into the rails to gain traction. This is aided by replacing wood railroad ties with stronger concrete ones, "allowing them to withstand the higher speeds. Also, the trains can pull more power from the electrical system than it would from diesel.

Maintaining the tracks is also more expensive than when using Maglev because more friction between the train and the track is created as the train's speed increases.

"Maintenance of the tracks has become a very high cost for the French and the Japanese high speed trains," said Albert Perdon, project manager of the California Maglev Project.

Magnetic levitation

Maglev, a technology invented in the United States in the 1960s but advanced in Germany and Japan, uses magnetic attraction repulsion to lift and drive trains.

The basis of power for both levitation and propulsion in Maglev is a motor that generates electric current through magnets embedded continuously throughout the rails. Slowing the current decreases the train's speed.

Two kinds of magnets drive Transrapid's propulsion and levitation aspects. Magnets placed along the sides of the train's axle are attracted to a magnetic force generated by a motor embedded into the rails.

Levitation magnets, also attached to the axle, keep the train balanced and elevate it at the height of several millimeters.

Maglev trains are nearly twice as fast as the New HSR system because they largely eliminate friction and vibration. It, too, requires new, straighter tracks to be laid to reach its maximum speeds of about 300 mph.

Japan uses two versions of Maglev, both called High Speed Surface Transport (HSST). Both are levitation and propulsion methods based on repelling magnets. Trains run in a channel cut in the track. Another distinction from Transrapid is that the train's levitation magnets are on the sides of the train rather than at the bottom of the train's axle.

HSST uses electricity-producing magnets on the train that play off currents in magnets on the railway. At high speeds, it lifts off magnetically and is levitated to roughly 15 centimeters. At lower speeds, it runs on robber tires.

Since the trains don't touch the track, Maglev systems generate less wear and tear.

Fast Tracks

Several new technologies are being employed in the development of high-speed transportation networks.

New High Speed Rail

An electrical system using new engines or existing diesel-powered trains that are converted to electrical power. They are powered by a current carried via wire cable running above the train, parallel to the track. Connecting poles at the top of each car pull power from the cable.

Transrapid Maglev

Magnets on either side of the train's axle are attracted to a magnetic force generated by a motor embedded in the tails. Levitation magnets, also attached to the axle, keep the train balanced and elevate it at the height of several millimeters.

HSST Maglev

High Speed Surface Transport uses a levitation method based on repelling magnets. Trains run in a channel cut in the track, and its levitation magnets are on the sides of the train.