U

For Untergrundbahn - underground train. Another interpretation of it is unabhängige Bahn, because unlike the Straßenbahn (street cars), the U-bahn network is designed to be independant of street circulation, and quite often circulates on the ground rather than under it anyways. This is not quite the case in Frankfurt, where the U-Bahn just has priority at street crossings.

 

Thank you everyone for your visits, faves and comments, they are always appreciated :)

Done