Sihltal Zürich Uetliberg Bahn

The history of the SZU dates back to two separate companies, which built the two railways that now make up the SZU. The first of these companies was the Uetlibergbahn-Gesellschaft (lit. 'Uetliberg Railway Society'), which opened its line from Zurich Selnau railway station in Zurich to near the summit of Uetliberg mountain, Zurich's Hausberg, in 1875. This was followed in 1892 by the Sihltalbahn company (SiTB, lit. 'Sihl Valley Railway'), which opened a line from Zurich Selnau station to Sihlwald. In 1897, this latter line was extended to Sihlbrugg and a connection with the Thalwil–Arth-Goldau line of the former Swiss Northeastern Railway (NOB).

In 1920, the Uetlibergbahn-Gesellschaft became bankrupt and was liquidated. Two years later, the Uetlibergbahn was taken over by the Bahngesellschaft Zürich–Uetliberg (BZUe). In 1923, the Uetlibergbahn was electrified using the direct current (DC) system, whilst the following year the Sihltalbahn was electrified using alternating current (AC).

In 1932 the SiTB took over the management of the BZUe, but the two companies remained in existence until 1973, when they were merged to form the SZU. In the meantime, in 1954, the SiTB had taken over the management of the Adliswil-Felsenegg cable car.

In 1990, the two lines were extended from their previous joint terminus at Zurich Selnau (until then a surface station) to a new terminus below Bahnhofplatz, adjacent to Zürich Hauptbahnhof (Zürich HB), named Zürich HB SZU. This extension involved the construction of a new rail tunnel from Selnau to Zürich HB, and a new underground intermediate station adjacent to the former terminus, Zurich Selnau. The underground platforms used at Zürich HB were already in existence, having been built prior to 1973 for a U-Bahn scheme that was ultimately rejected by voters. Once the new extension had been opened, the former terminus at Selnau was redeveloped and little evidence of it is now visible.

In 1995, the company took over responsibility for bus services in parts of the district of Horgen through which the Sihltalbahn runs.

In 2006, after 109 years, the Sihltalbahn stopped servicing Sihlbrugg and Sihlwald, previously the penultimate station, became the new terminus.

Rail network

The SZU continues to operate the original Uetlibergbahn and Sihltalbahn lines. The two lines share a common double-track section between Zürich Giesshübel and Zürich HB SZU, with the final approach being in a tunnel, partly under the Sihl river. A dedicated pair of underground platforms (tracks/Gleis 21 and 22) are used at Zürich Hauptbahnhof (Central Station), with no rail connection to the rest of the station. The platforms are physically connected via the ShopVille underground mall.

Also operated is a connecting line from Giesshübel to the Swiss Federal Railways at Zürich Wiedikon, although this is normally only used for freight traffic. It is occasionally also used by passenger trains, for example if the regular route From Zürich HB to Zug via Thalwil becomes temporally inoperable. In all, the SZU network measures 30.06 km (18.68 mi): 19.7 km (12.2 mi) as part of the Sihltalbahn (including the Wiedikon–Giesshübel line) and 10.36 km (6.44 mi) of the Uetlibergbahn.

Both railway lines are constructed to 1,435 mm (4 ft 8+1⁄2 in) standard gauge and both are electrified using the standard Swiss mainline system of overhead lines at 15 kV 16.7 Hz AC. Until 2022, the Uetlibergbahn was electrified using overhead lines at 1200 V DC. In order to avoid conflict on the shared railway section, the Uetlibergbahn used an overhead line offset from the centre of the track, and its cars were equipped with specially designed, laterally displaced pantographs.

Operations

Railways

The passenger services on the two lines form part of the Zurich S-Bahn, with the service over the Sihltalbahn to Sihlwald branded as the S4 and the Uetlibergbahn branded as the S10. The Sihltalbahn also includes a nighttime service during weekends (SN4). At Zürich Hauptbahnhof (Zürich HB), all SZU services depart from the subsurface Zürich HB SZU station located below Bahnhofplatz.