It took a long time to complete the rail line from Freiburg/Breisgau to the Black Forest via the Höllental Line. At first, the technical options at that time or an extremely costly routing hampered railroad construction. Since a purely adhesion rail line was too expensive, the plan was to conquer the steepest section between Hirschsprung and Hinterzarten on a path with the help of a cogwheel rack. This variation was realized at the start of the 1880s under the leadership of the brilliant railroad builder Robert Gerwig. The steep section between Hirschsprung and Hinterzarten at up to 5.5% was equipped with a cogwheel rack based on the Bissinger-Klose System up to the Posthalde Station at a length of 6,525 meters / 4.078 miles. After over three years of construction time, continuous operation between Freiburg and Neustadt/Black Forest was finally started on May 23, 1887 in the presence of the Grand Duke of Baden. A continuation to Donaueschingen had to wait almost ten years. Finally, the decision was made to use this variation via Löffingen. A curving and longer right-of-way as accepted in order to tie as many communities as possible to the so-called “Rear Höllentalbahn Line” than what would have been necessary on a more direct path. Train operations between Neustadt and Donaueschingen finally began on August 20, 1901. At the start of the Thirties, the DRG decided to electrify the Höllentalbahn Line between Freiburg and Neustadt as well as the Dreiseenbahn Line. In a departure from the customary railroad current system of 15 kilovolts / 16.7 Hertz, the plan here was to use an experimental electrical operating system with the so-called industrial current of 20 kilovolts and 50 Hertz, which was then done until the fall of 1935. There were problems starting in mid-1956, when the two current systems met in the Freiburg Station after electrification of the Baden main line Mannheim – Basle. In order to eliminate Freiburg as a system change station and to maintain efficient operations, the DB decided to convert both lines by May 20, 1960 to the standard current system of 15 kilovolts and 16.7 Hertz. Yet since the spring of 2018, big changes are casting their shadows. As part of the comprehensive plan “Breisgau S-Bahn 2020”, the German Railroad has begun extensive construction work to modernize and expand the infrastructure on the Höllentalbahn Line. Starting March 1, 2018, the western section Freiburg – Neustadt/Black Forest was completely closed in order to enable extensive conversion work for S-Bahn operations. This included new catenary installation on many parts, new 55 cm / 22” inch high, 210 meter / 683 foot long and at least 2.50 meter / 8 foot wide platforms including handicapped access at all stations as well as overhauling the track installations including improvements to the infrastructure in order to enable better containment of disruptions and delays in the future. Starting April 1, 2019 continuous operation from Freiburg to Neustadt will be possible again. The Rear Höllentalbahn Line between Freiburg and Donaueschingen has also been closed since May 1, 2018 for these measures. It is being electrified, whereby the track in the five tunnels on the line in particular is being prepared for installation of catenary by lowering the track by up to 70 cm / 27-1/2”. Since part of the construction sites are difficult to access, a large part of the transport of material is being done by rail. Of course, all of the stations on the Rear Höllentalbahn Line are being expanded without barriers and the track installations are being overhauled. These measures are supposed to be completed by October 31, 2019. The new S-Bahn concept on the Höllentalbahn and Dreiseenbahn lines will then take effect with the change in schedules in December of 2019. Instead of the previous bi-level shuttle trains and diesel-powered rail cars, modern three or four-part Alstom “Coradia Continental” type (class 1440) electric-powered rail cars will then be running. With the electrification of the Rear Höllentalbahn Line, continuous train connections on hourly schedules will be possible in the future: from Villingen via Donaueschingen, Löffingen, Neustadt, Hinterzarten, and Kirchzarten to Freiburg as well as further to Breisach or Endingen am Kaiserstuhl.