What is "stadtbahn"

A (; German for "city railway"; plural ) is a tramway or light railway that includes segments built to rapid transit standards, usually as part of a process of conversion to a metro railway, mainly by the building of metro-grade tunnels in the central city area.

Stadtbahn networks were mostly implemented in the 1960s and 1970s with the long-term goal of establishing a full-scale metro system, but by the 1980s virtually all cities had abandoned these plans due to the excessive costs associated with converting the tramways. Most Stadtbahn systems are now a mixture of tramway-like operations in suburban and peripheral areas and a more metro-like mode of operation in city centres, with underground stations. This Stadtbahn concept eventually spread from Germany to other European countries, where it became known as pre-metro.