Tram-train

Tramcars are adapted to be capable of running on streets like an urban tramway but also be permitted operation alongside mainline trains.

This concept is often referred to as the Karlsruhe model,[1] and it has since been adopted in other cities such as Mulhouse in France[1] and in Kassel, Nordhausen and Saarbrücken in Germany.

[2] An inversion of the concept is a train-tram – a mainline train adapted to run on-street in an urban tramway, also known as the Zwickau Model.

The tram-train often is a type of interurban[3] — that is, they link separate towns or cities, according to George W. Hilton and John F. Due's definition.

The Karlsruhe and Saarbrücken systems use "PZB" or "Indusi" automatic train protection, so that if the driver passes a signal at a stop the emergency brakes are applied.