The Höllentalbahn line starts in Freiburg (Breisgau) and ends in Donaueschingen. Most of the line is a single-track line, only the track section from Freiburg (Breisgau) to Freiburg-Wiehre is a double-track line. Between the stations Himmelreich und Hinterzarten the line, which is classified as a main line, has a gradient of up to 57.14‰ which makes the Höllentalbahn the steepest main line of Germany. The track of the western Höllentalbahn, i.e. line 4300 W, has a length of nearly 36 kilometres. It is completely electrified from Freiburg main station to Neustadt station and was constructed as a special construction type E 28 (Einheitsfahrleitung (standard catenary) 1928) around 1936.
The range of services includes the planning up to the complete construction of the Re100 / 100 K type catenary system. The works were carried out during a complete closure of the track.