It's called 'RUF." Rapid, Urban, Flexible. It's an electric car when you need to run short, individual errands. And it becomes part of a highly efficient, non-polluting "train" as it enters an elevated, automated guideway. For more than a dozen years, inventor Palle Jenson has been almost evangelical in his belief in this dual mode transportation system. A prototype of the RUF electric cars is in constant development at the Engineering College of Copenhagen.