They brought the world the bullet train. Now engineers in Japan have broken the world train speed record for the second time in a week - topping 603kph.



Central Japan Railway has been testing its advanced superconducting Maglev train at Yamanashi west of Tokyo.

After decades of research and development officials are confident their technology will shape a new generation of trains.



"This train is set up the same way we will use it commercially," said Yasukazu Endo from Central Japan Railway.

"We have seen the comfort of passengers at this high speed has improved. I think such test results should lead to a stable commercial use in the future."



The test is part of an ambitious plan to build a $47bn high-speed line between Tokyo and Nagoya. If completed as planned in 2027, the 280km could be travelled in around 40 minutes. Much of the route will be through underground tunnels.



"When they are going fast, over 500kph, they do make a lot of noise," said Christopher Hood, a writer on Japan's high-speed trains.



"By having them deep underground - at least 40 metres - it's thought they are out of the way.

"And you don't have to worry about trying to navigate around corners because you can effectively draw at track point to point and you can almost have an exact straight line."



The train's magnetic levitation, or maglev technology, is based on simple physics - how opposite magnetic poles attract and like poles repel each other.

By chilling down powerful electromagnets engineers are able to lift the train about 10 centimetres off the ground.

Then another set of electromagnets is used to push it along. Because it is riding on a cushion of air there is little friction, making it a smooth ride and potentially very fast.



Overseas customers



Japan is hoping to sell its high-speed train technology to the US.



Last April, Prime Minister Shinzo Abe took a ride on the maglev train with US Ambassador to Japan Caroline Kennedy.

Central Japan Railway is hoping its maglev technology will be used on a planned high-speed line between Washington and New York. Its push to find overseas customers is an attempt to recover some of its research and development costs.



"China is now becoming a big player and is looking to export the technology," said Hood. "Much of which it has imported from Japan and Germany.



"Although the Germans have a [maglev] system it's starting to look as if the Japanese may be slightly in the lead in their technology and their technology might be superior."



Critics of the Japanese maglev system say the technology is too expensive, power-intensive and potentially unsafe.

They say an event like an earthquake could knock the train off its line and at such high speeds it would have a devastating effect.

Japanese engineers say their early warning system can deal with this and that continuing tests will prove the safety and efficiency of this new technology.