>>1285535>At this point, you just might as well build an MRT line.Except many West German cities didn't.
A number of cities, like Cologne, Düsseldorf, Bielefeld and Frankfurt am Main developed a pre-metro system using what was essentially the same trams that were in use in other cites, similar to the rolling stock on the Karlsruhe Model.
The intention was to build a number of underground stations in the inner city with tunnels through it and have the rolling stock emerge into either dedicated RoW or onto street running once out of the inner city. The plan would be to eventually build out the metro system and then eventually switch to heavy rail MRT. This resulted in a number of cities over-engineering the underground stations and tunnels in the inner city to MRT standards, even if the tunnel and underground section only was 3-4km long, sometimes shorter.
This became known as Stadtbahn (not to be confused with S-Bahn which is thought to either abbreviate from Stadtbahn or Schnellbahn). Some cities even insist that their pre-metro Stadtbahn is a fully fledged U-Bahn (*cough* Frankfurt *cough*).
Berlin, Nuremberg, Munich and Hamburg all have heavy rail MRT systems, and they have more or less set the standard for MRT and the "U-Bahn". In the case of Berlin and Hamburg, their S-Bahn networks can even be considered MRT, just not underground MRT (although both cities have large sections of underground tunnels for certain S-Bahn lines).
