The construction and operation of these lines remained with the Siemens & Halske AG, while BOGESTRA itself initially took only functional control.

BOGESTRA's new Stadbahn line would be operated on standard gauge rail with high platform stations in its own right-of-way using Stadtbahn B train cars.

The first Stadtbahn section was opened on 2 September 1989 between Bochum Central Station and Castle Herne Strünkede as Line U35.

This was also the first inter-city subway tunnel in Germany, because the city boundary between Bochum and Herne is crossed underground on Line U35.

Planned sections of the U35 line northwest to Recklinghausen and southeast to Witten were never implemented due to the associated costs to these respective municipalities.