line used modern double-decker rolling stock pulled by DB Class 143 locomotives. Exceptions were the two long distance Trains that brought their regular locomotives to the Höllentalbahn: Regional-Express Kleber-Express Freiburg-Munich did no longer change its locomotive in Neustadt 1988-2003 as last remaining direct train between Freiburg and Donaueschingen thus the diesel DB Class 218 operated also on the electrified part of the route on this train. The InterRegio Höllental Emden-Seebrugg ran with its DB Class 101 1996–2002. On the stretch of line between Neustadt and Donaueschingen DB Class 215 operated the trains until they were replaced by DB Class 628 in 1988 ending direct connections over Neustadt. From the 2000s onward DB Class 611 took over until this part of the Höllentalbahn got electrified in 2019. Since then Alstom Coradia Units (DB Class 1440) operate the S1 Breisach-Seebrugg and S10 Freiburg-Villingen lines. Development during the era of the German National Railway (1919–1945) On 14 December 1927 the old Ravenna bridge that crossed the Ravennaschlucht (Ravenna ravine), close to Hinterzarten, was replaced with a new viaduct, because it could not cope with the demand anymore. With the construction of the new viaduct, the railway section of the Höllentalbahn was straightened in that area. The costs were about , and only the abutments are still leftovers of the old bridge. The Ravenna tunnel which follows immediately after the bridge was originally 85 metres long. It was partially split open so that nowadays it only has a length of 47 metres. At the beginning of the 1930s, the Höllentalbahn between Freiburg main station and Freiburg- Littenweiler was relocated, so that the station of Freiburg-Wiehre had to be moved as well. 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. Furthermore, the intersection with the already existing line to Günterstal of the Freiburg im Breisgau tramway, which existed since 1901, could be discontinued. 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 tram and the line-keepers lodge got shattered while the tram driver, the conductor and the only passenger got slightly injured. Two new tunnels had to be built for the new line: the one going through the