Maglev Train (Magnetic Levitation Train)

Magnetic Levitation Train or Maglev Train, a high-speed ground vehicle levitated above a track called a guideway and propelled by magnetic fields (see Magnetism). Magnetic levitation train technology can be used for urban travel at relatively low speeds (less than 100 km/h, or 60 mph); a short-distance maglev shuttle has been operating in Britain since 1984, between Birmingham's airport and railway station. However, the greatest worldwide interest is in high-speed maglev systems. Train speeds of 517 km/h (321 mph) have been demonstrated by a full-size maglev vehicle in Japan, while in Germany a maglev train has run at 435 km/h (270 mph).

Two different approaches to magnetic levitation train systems have been developed. The first, called electromagnetic suspension (EMS), uses conventional electromagnets mounted at the ends of a pair of structures under the train; the structures wrap around and under each side of the guideway. The magnets are attracted up towards laminated iron rails in the guideway and lift the train. However, this system is inherently unstable; the distance between the electromagnets and the guideway, which is about 10 mm (3/8 in), must be continuously monitored and adjusted by computer to prevent the train from hitting the guideway. A 31.5-km (19.6-mi) track in Emsland, Germany, is currently testing this approach.

The second design, called electrodynamic suspension (EDS), uses the opposing force between magnets on the vehicle and electrically conductive strips or coils in the guideway to levitate the train. This approach is inherently stable, and does not require continued monitoring and adjustment; there is also a relatively large clearance between the guideway and the vehicle, typically 100 to 150 mm (4 to 6 in). However, an EDS maglev system uses superconducting magnets, which are more expensive than conventional electromagnets and require a refrigeration system in the train to keep them cooled to low temperatures (see Superconductivity). A 7-km (4-mi) track to test this system, based in large part on designs developed in the United States in the late 1960s and early 1970s, is in use in Miyazaki, in Japan. Both EMS and EDS systems use a magnetic wave travelling along the guideway to propel the maglev train while it is suspended above the track.

Maglev systems offer a number of advantages over conventional trains that use steel wheels on steel rails.

Because magnetic levitation trains do not touch the guideway, maglev systems overcome the principal limitation of wheeled trains-the high cost of maintaining precise alignment of the tracks to avoid excessive vibration and rail deterioration at high speeds. Maglevs can provide sustained speeds greater than 500 km/h (300 mph), limited only by the cost of power to overcome wind resistance. The fact that maglevs do not touch the guideway also has other advantages: faster acceleration and braking; greater climbing capability; enhanced operation in heavy rain, snow, and ice; and reduced noise. Maglev systems are also energy-efficient on routes of several hundred kilometres' length, they use about half as much energy per passenger as a typical commercial aircraft. Like other electrical transport systems, they also reduce the use of oil, and pollute the air less than aircraft, diesel locomotives, and cars.

Current plans for high-speed maglev systems include a 283-km (175-mi) route from Berlin to Hamburg, which has been approved by the German parliament; commercial operations are scheduled to begin by 2005. In Japan, a 43-km (27-mi) maglev test track is under construction in Yamanashi Prefecture, about 100 km (60 mi) west of Tokyo. When tests on the latest maglev vehicle have been completed, the test track is planned to be extended to Tokyo and Osaka. This new commercial line will relieve passenger demand on the Shinkansen high-speed train, which currently operates at peak speeds of 225 km/h (140 mph).
In the United States, much of the interest in maglev systems has been initiated at the state level, with plans developed in Florida, California, Nevada, New York, and Pennsylvania. Studies completed by the federal government in 1993 concluded that the potential benefits of a maglev system justified starting a national development programme.