Because of this and the steady decrease of traffic between Neustadt and Donaueschingen the route did not represent an operational unit anymore.

The missing section was electrified until the end of 2019 in the course of the project “Breisgau-S-Bahn 2020”, in order to enable direct trains from Breisach via Freiburg, Neustand and Donaueschingen to Villingen.

The 7.2 km (4.5 mi) section of the line between Hirschsprung and Hinterzarten has a maximum gradient of 5.5%, and was initially operated as a rack railway on the Riggenbach system.

This enabled the original route, which passed closer to the city centre and over congested level crossings, to be closed.

[4] In 1936, the Deutsche Reichsbahn electrified the line between Freiburg and Neustadt, installing a 20 kV, 50 Hz AC.

Therefore, in 1960, the electrified section of the Höllentalbahn was converted to the standard 15 kV, 162⁄3 Hz system used throughout the German railway network.

1996–2019, the electric line used modern double-decker rolling stock pulled by DB Class 143 locomotives.

The relocation was made in order to avoid the intersection with the Rheintalbahn, to create a bridge instead and especially to get rid of the railroad crossings in the city area.

There was a severe accident on 12 October 1916 because a tram, which was heading into town, disregarded the closed barrier in the darkness and collided with a railroad train going uphill.

The section of the line between Hirschsprung and Hinterzarten has a steep maximum gradient of 5.5%, betraying its origin as a rack railway.

[2] Further on, between Neustadt and Donaueschingen, the viaduct at the former Kappel Gutachbrücke station [de] crosses the Wutach at the beginning of its long gorge.