One blue-sky idea is the Aero-Train - a plane-like vehicle which travels at up to 350km/h (220mph) just 10cm above the ground.

The vehicle uses a technology known as ground-effect which removes the friction that makes conventional rail transport less efficient and uses aerodynamics to reduce drag.

Its speed relies on aerodynamics similar to those used in a plane or a hovercraft, using the air as a cushion to prevent it from touching the floor.

While currently in prototype, developers at the Tohoku University in Japan have already demonstrated the idea and hope it can be in public use by 2020.

But there are trains in use right now that never touch the ground.

Maglev trains, most famously in use in China between Shanghai Pudong International Airport to an interchange with the Shanghai Metro, operate just centimetres from the track’s surface.

The train is held from the ground by a magnetic field - the term maglev is short for magnetic levitation - and powered by motors that, without as much friction, allow it to go at very high speeds.

@http://news.bbc.co.uk/2/hi/programmes/click_online/9617577.stm

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