Cybertran is a new concept in mass transportation developed at the Idaho National Engineering and Environmental Laboratory. It is a form of rail transportation that uses many small vehicles instead of a few large ones; they operate on small, elevated tracks under complete computer control. At a Cybertran station, you would select your destination and a car would be called for you, just as an elevator comes when you select your desired floor. These cars could travel throughout a city, taking you fairly directly to your destination, or even to a different city (using much higher speeds for the intercity route).
More pictures and details are at http://www.cybertran.com.
A similar system is being designed for the city of Cardiff, Wales; an article describing it can be found at http://news.bbc.co.uk/hi/english/uk/wales/newsid_1765000/1765120.stm and a more detailed paper is at http://atg.fen.bris.ac.uk/picet.htm.
Also see the /HighSpeedRail page.