The Tokyo University's Institute of Industrial Science, with the help of amusement ride firm Senyo Kogyo, is testing a prototype roller coaster train for commuter transportation.
The train, which has no engine, coasts along a tubular track at a test facility in Chiba, about 40 kilometres from the centre of Tokyo.
The train's speed is controlled by aerodynamics and "vertical curves" – sections of track that form the transition between two sloping segments. The train is set in motion and slowed at stations by rotating wheels between the rails that catch a fin underneath the train. It can reach s;eeds of up tp 60 kilometres an hour.
The lack of an engine makes the train extremely light, so the energy required to propel it is small and emissions are low.
A number of municipalities in Japan have shown an interest in the system, including communities hit by last year's devastating earthquake and tsunami.