The principal of a Magnet train is that floats on a magnetic field and is propelled by a linear induction motor. They follow guidance tracks with magnets. These trains are often refered to as Magnetically Levitated trains which is abbreviated to MagLev.
A vactrain is an exotic, as-yet-unbuilt proposal for future high-speed railroad transportation. This would entail building maglev lines through evacuated (air-less) tunnels.
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Vactrain - Wikipedia, the free encyclopedia
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Maglev (transport) - Wikipedia, the free encyclopedia