Donautalbahn
The high expectations, which the military had placed in the Danube Valley Railway in connection with the other railways in the southwest of Germany, were not met in either World War I or World War II. Up until World War I, there were just a few efforts at expanding the Danube Valley Railway from the single-track formation it had featured since 1890. In 1912, the connection to the new shunting yard for the city of Ulm, which was located in Söflingen, was expanded by the Royal Württemberg State Railways to twin tracks on the 3-kilometre-long section between Söflingen and Ulm Hauptbahnhof. By 1913, twin tracks had been laid to Herrlingen. Also prior to World War I, the state of Württemberg had planned to expand the section between Tuttlingen and Immendingen, which was also used by long-distance trains on the Stuttgart–Hattingen railway, to feature twin tracks. The advent of World War I put a stop to these plans, and the plans were then cancelled in favour of the construction of a new railway between Tuttlingen and Hattingen in Baden, which had trains from the Gäubahn running on it, starting in 1934. The section of the Danube Valley Railway between Tuttlingen and Immendingen therefore saw much less traffic, and has been kept as a single-track rail line to today. The expansion of the Schwarzwaldbahn (Baden) to feature twin tracks, which was completed in 1921, had the side effect of expanding the westerly section of the Danube Valley Railway, between Immendingen and Donaueschingen, to feature twin tracks soon after the end of World War I.