UK to Develop Lightweight Tram-Train System

Network Rail is in the midst of drawing up plans to develop "a fleet
of innovative lightweight trains that operate seamlessly between
traditional train lines and tram networks" in Britain.  Due to the vehicles lightweight, they can brake and accelerate much faster than existing trains, signifigantly reducing time wasted at stops as well as creating less wear and tear on the railway infrastructure. 

The Telegraph reports:

The scheme is being presented as a way of streamlining
the transport network around major cities - the same vehicle can take
passengers across long distances between cities, but then enter urban
areas and drop them off nearer their destination, just as a bus or tram
would.

Similar trams are already being utilized in Kassel, Germany.

The Telegraph: UK in Line for New Tram-Trains