The planning of a connection to Friedberg as a continuation of the
Homburg Railway began as early as 1868. However, it was not clear whether the connection to the
Main-Weser Railway or a line to the
Taunus would be built first. It was decided to build the Usingen Railway (
Usinger Bahn), now called the
Taunusbahn (
Taunus Railway). Construction of the Friedrichsdorf–Friedberg link began in 1898 and the line was put into operation on 15 July 1901. The trains started at the terminus of
Homburg vor der Höhe (also called
Homburg Neu (new) station) on the lower Louisenstraße, which had been the starting point of the Usingen Railway since 1895. At the request of the emperor,
Wilhelm II and to increase the capacity of the line from Frankfurt to Bad Homburg and from Friedrichsdorf to Friedberg, the line was upgraded to two tracks between 1907 and 1912 and a through station was built in Bad Homburg. After the upgrade of the line, it was used by the trains of the
Bad Nauheim–Wiesbaden railway (
Bäderbahn), consisting of
Eilzüge (fast-stopping trains) from
Wiesbaden via
Höchst and Bad Homburg to
Bad Nauheim and a daily pair of
Durchgangszüge (through trains) on the
Berlin–Wiesbaden route. Due to decreasing profitability, the second track was dismantled after the end of the First World War. With the takeover by the
Nazis, it was restored for the planned Friedberg–Hungen–Alsfeld–Hersfeld line. During the Second World War, a bridge at the entrance to Friedberg station that carried the second track to the Main-Weser Railway was destroyed. Subsequently, the second track was dismantled, starting with the Friedberg–Rosbach section, which was completed by 1950, and later with the Rosbach–Friedrichsdorf section, which was completed by 1968. This also made the
block post at Straßheim at the original ladder junction at the entrance to the station superfluous. Based on the width of the embankment and the bridges, the location of the former second track is still largely recognisable and a piece of it was maintained as a
catch point at the junction to the industrial siding in Rosbach. The bridge over the
line to Hanau still exists and it now carries a freight connection from the Main-Weser Railway to the goods yard above the station. While the Frankfurt–Friedrichsdorf section was electrified and signalling control was transferred to the new centralised
relay interlocking in Bad Homburg, the
mechanical interlocking on this line was initially preserved and Rosbach was rebuilt in 1985 as a halt (
Haltepunkt, that is without points). Also the sections of track became more operationally distinct at the end of the 20th century: the tight timing and the introduction of
S-Bahn electric multiple units to Friedrichsdorf contrasted with the operations over the Friedrichsdorf–Friedberg line, which were mainly consisted of push-pull trains composed of
Silberling (n-coaches) hauled by
V 100 locomotives and
Uerdingen railbuses; these were replaced by
class 628 diesel multiple units, but services ran ever less frequently. The class 628 sets when not operating were usually stored outside Friedrichsdorf station towards Seulberg on a track to a no longer connected marshalling yard hump. With the commencement of S-Bahn operations to Friedrichsdorf and also to Friedberg, the normal Friedberg–Bad Homburg–Frankfurt through services were finally discontinued, although some long-distance trains still used the line. A 30 or 60-minute interval service was only re-introduced with the establishment of the
Rhine-Main-Verkehrsverbund. After previous considerations of closing the line, the
Butzbach-Licher Eisenbahn (BLE), a subsidiary of the
Hessische Landesbahn, took over operations on 24 May 1998. New
Stadler GTW railcars were procured for this operation. Due to its success and rising passenger numbers, there were also plans to restore the second track or even to electrify it. Only a few bridges would have had to be widened. A footbridge in Friedrichsdorf parallel to Färberstraße was increased in the meantime as part of its renewal to allow for a possible overhead line. However, more economical modernisation of the line was chosen. At the beginning of 2002, the tracks were completely renewed with
Y-shaped sleepers. The stations were also renovated and a new station,
Friedberg Süd, was added. The
Rosbach vor der Höhe station, which is about halfway along it, was upgraded to become the crossing station, where trains could pass. The crossing in Rodheim was abandoned and the station was rebuilt as a halt with a single track. Finally, the signalling technology was modernised. Thus, the railway was downgraded from a main line to a branch line. For part of the construction work, traffic had to be blockaded for several weeks. On 21 April 2002, the re-commissioning was celebrated with two commuter trains shuttling over the line (a steam train and a GTW set). Next day, regular services commenced under a new timetable. This included not only an extended period when half-hourly services ran on weekdays but also a full service on the weekend. In addition, some connection times at the end stations were changed. The replacement of the bridge over the former Federal Highway 3 at the halt of Friedberg Süd was carried out in July 2017 during a three-week full closure of the line. == Route==