Danube Valley Railway
In 1934, the name started to be used in yet another form: When the connection between Tuttlingen and Hattingen was completed, this line then connected the Gäu line to the section of the Black Forest line between Hattingen and Singen, forming a contiguous railway between Stuttgart and the Swiss border near Singen. This entire railway then adopted the term Gäubahn. The section of railway running between Tuttlingen and Immendingen, which had been replaced on the Gäubahn by the new section Tuttlingen-Hattingen, was assigned exclusively to the Danube Valley Railway ("Donautalbahn", see Tuttlingen–Inzigkofen railway).