People at Tokyo University have released details of a concept they've been working on which sees a rollercoaster being used as a city transportation system. Imagine a monorail that's actually a cred.
The system has been named "Eco-Ride" as its primary concern is being an energy efficient form of transport. The theory being that you only need to power the lift hill (and potentially a few "tyre launch" type sections) then gravity does the rest. Some of the areas they have in mind to install this system would apparently also lend themselves to a "terrain coaster" type layout.
They are currently working on prototypes and are hoping to see the real thing installed in 2014. Some areas of Japan, including those worst hit by the Earthquake/Tsunami, are reportedly interested.
The system is being developed in conjunction with ride manufacturer Senyo Kogyo. They've got 55 coasters listed on RCDB (http://rcdb.com/r.htm?ot=2&co=6957) the best known of which is probably 'Diving Coaster: Vanish'
http://www.newscientist.com/article/mg2 ... train.html