Sihltalbahn is a part of the SZU or Sihltal - Zürich - Uetliberg -Bahn Gruppe. The SZU is a combination of two Zürich region private railroads, the Sihltalbahn, which operates the S-Bahn line S4 from Zürich up the valley of the Sihl river and the Uetlibergbahn, which climbs steeply up the hillside of Uetliberg, landmark of Zürich. Synergy between these two lines was originally modest: although both are normal gauge railroads, the Sihltalbahn was electrified with the usual 'big railroads' 15 kV AC, 16,7 Hz whereas the Uetlibergbahn used the tram-like DC 1200V DC - and with a very exotic aerial (please see the section of Uetlibergbahn). The combined companies that made up SZU split again in 1999-2000 and later rejoined again. Now in 2023-24 the electric system of the Uetlibergbahn will be changed to be the same 15 kV AC as what the Sihltalbahn has been using, so it can be said that finally these two companies are growing together and they can finally start using the same trains.

Sihltalbahn is a 28 km long piece of normal gauge, 15 kV AC railroad from Zürich up the Sihl valley, connecting nowadays a series of suburban areas to central Zürich. The typical Sihltalbahn train is either a doubledecker EMU type train or a locomotive led, short commuter train with a modern Re 4/4 (Re 456) locomotive and one or two red doubledecker coaches in its middle plus one or two single deck coaches, the last one a steering cab coach. Although a modern suburban railroad, the Sihltalbahn has traditions: the track was opened for service already 10.5.1875 and still today operates several historic trains in addition to the busy city commuters.

This train is a so called DPZ train (doubledecker pendeling train). SBB bought 115 of these beginning 1990 for serving the Zürich area suburban routes and in 2008 SZU bought two DPZ trains from SBB for use on the Sihltalbahn route. This is one of the two. Officially this one is still Re 450 551 according to the naming convention of SBB, but SZU has also used "Re 456 551" and now lately just "Re 551" as its unoffial "name". These are fixed sets of one locomotive and three doubledecker coaches so that the last coach has a steering cab and the trains are used in push-pull mode.
Photo from Langnau station 15.5.2023 by Ilkka Siissalo.

A typical SZU Sihltalbahn S-Bahn train in 2023 seen from behind. These are push-pull trains with normally an Re 4/4 V (= Re 456) locomotive at the end towards Zürich and a steering cab coach towards Langnau, the other end of the S4 line. Here this steering cab coach has been taken from an approximately 35 years old SBB NPZ (Neue Pendelzug) train which has been quite heavily refurbished or rather to be more eaxct totally rebuilt. The passenger space floor is much much lower now and approximates low-floor trains, the cab has received its own doors, new airconditioning devices have been added on the roof which has been completely rebuilt, the doors are different than what they used to be... And the next wagon, built much, much later by Stadler to match this one looks very much the same although it is some 30 years younger. Notice also how the train consists of a locomotive plus two double decker wagons (barely visible here) and only then these two single decker coaches.
Photo from Langnau-Gattikon station 15.5.2023 by Ilkka Siissalo

A second picture of the same train. Looking at only these wagons it seems almost impossible to believe the fact that the wagon on the right (the steering cab coach shown above) is at least 30 to 35 years older than the next wagon. But it is. The next wagon is a later addition by Stadler to make this train abide to the new Swiss law saying that every train, tram or similar will have to have at least some part which is officially "accessible", meaning low-floor. The new middle wagon is.
Photo from Langnau-Gattikon station 15.5.2023 by Ilkka Siissalo

Two next wagons of the same train as shown above. The two first wagons after the locomotive were double-decker coaches, identical with the ones that DB has been using in Germany for years and years and built in Görlitz, Germany. But also these wagons have now been recently rebuilt and they look like new again. All the orange colourings that they used to have has vanished during the renovation, so now they are totally red with just white doors.
Photo from Langnau-Gattikon station 15.5.2023 by Ilkka Siissalo

This was the locomotive of the same train shown here wagon by wagon. This is an Re 456 class machine no.543 or according to SZU's own shorthand just "Re 543". These were fifth generation Re 4/4 locomotives and they were so new that they used thyristor technology. SBB bought only four prototype machines, older than this one, and classified them as Re 4/4 IV and later sold all four to Südostbahn but never bought these newest generation machines. Several private companies however wanted to grasp the new technology and ordered these machines. SZU Sihltalbahn and SOB Südostbahn, AB Appenzeller Bahnen, BT Bodensee-Toggenburgbahn and VHB Vereinigte Huttwil Bahnen (today part of BLS Lötschbergbahn) bought these very modern machines and have been very happy with them. After all the owenership changes only SZU and SOB have them today.
Picture from Langnau-Gattikon 15.5.2023 by Ilkka Siissalo.

Another one of SZU's Re 456 (or Re 4/4 V according to the old notation) locomotives, parked in front of a similar S-Bahn train like the one displayed up here wagon by wagon. This one was clearly waiting for the next morning's rush hour traffic to begin. This one was the Re 456 no.101. This one had not yet been thoroughly modernised and repainted as you can tell from the somewhat faded red paint.
Picture from Langnau-Gattikon 15.5.2023 by Ilkka Siissalo.

This was the BDe 4/4 no. 94 (or BDe 576 594 in the new numbering scheme) of SZU Sihltalbahn. This EMU was orderer from SWS/MFO in 1968. It weighed 58 tons and had a maximum speed of 70 km/h. SZU had four of these EMUs, which typically ran up to four coaches long trains from Zürich to Langnau. Today these trains are no longer in use.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo

A view of the BDe 4/4 no. 94 (or BDe 576 594 in the newer notation) of SZU Sihltalbahn, in front of a train ready to leave towards Zürich.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

A closeup of the BDe 4/4 no. 94 (or BDe 576 594) of SZU Sihltalbahn, showing the cargo department. Rounded corners were very typical of the design of EMU trains of the 1960´s.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

BT995 coach of the SZU Sihltalbahn with a driver´s cab in the other end of a train led by the BDe 4/4 EMU no.94. These matching coaches were also from the late 1960´s.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

A bit later design, a typical 1970´s coach with a driver´s cockpit of the SZU Sihltalbahn. This one was used to steer a 3 coach train powered by a pushing Re 4/4 locomotive.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

Re 4/4 no. 44 or nowadays officially Re 456 544 of the SZU Sihltalbahn. This type was developed based on the SBB Re 4/4 IV series, but designed for the small private railroads. It was their first locomotive based on thyristor technology. This type was used by Sihltalbahn, Bodensee-Toggenburgbahn BT, Südostbahn, Appenzeller Bahnen and EBT and it became quickly famous and popular. It was built by SLM and ABB in 1993. The locomotive weighs 69 t and has a maximum speed of 130 km/h - a speed it never needs on the short Sihltal line. The text painted promotes the SZU website www.szu.ch.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

Re 4/4 - or as the notation now goes, Re 456 - no.546 is a very typical SZU Sihltalbahn locomotive, used especially during rush-hour intensive traffic with long trains including doubledecker coaches.
Picture from SZU's underground station under the Zürich main station 31.12.2007 by Ilkka Siissalo.

To keep trains short, doubledecker coaches are widely used in Swiss regional trains. The Sihltalbahn trains are short anyway and they usually only have just one double decker coach in the middle of the train.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

A typical SZU Sihltalbahn train during afternoon rush hours. On the right, far outside of the picture area, was an electric locomotive of the type Re 456, then two new Stadler made low-floor coaches, two doubledecker coaches and at the end of the train again two new singledecker Stadler coaches, the last one with a driver's cab. This picture shows one of the new Stadler made single decker coaches.
Picture from the underground SZU station under Zürich main station 2.10.2015 by Ilkka Siissalo.

The same train as in the picture above. These were the two doubledecker coaches in the middle of the train. They are similar to the ones that DB uses in Germany and they have been built by Bombardier in Germany.
Picture from the underground SZU station under Zürich main station 2.10.2015 by Ilkka Siissalo.

SZU Sihltalbahn Re 4/4 no. 46 and 47 parked side by side waiting for the busy morning traffic to begin. Unlike their sibling, the no. 44, these two still show the older SZU painting, the old company logo and use the old numbering notation. Their "names" in the new schemes would be Re 456 546 and 547 respectively. Each one had a train of 4 coaches, one of which was a doubledecker coach.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

An unidentified SZU Sihltalbahn coach from the 1970´s with a driver´s cab. This one was used to steer an older train led by one of the SZU BDe 4/4 (new numbering BDe 576 or 577) EMU´s. These older trains were in 1999 used mainly at rush hour times.
Photo from Langnau station 30.5.1999 by Ilkka Siissalo.

A historic SZU Sihltalbahn train, in 1999 used as a movable base for railroad construction workers. The locomotive Ce 4/4 no 41. (old numbering De 3/4) is from 1926, a famous "small crocodile" type - the only one of its kind ever and today a real rarity. It was a further development from the famous SBB "crocodiles" of type Ce 6/8. It generated 490 kW of power, which in the 1920s was a a miracle for such a small locomotive.
Photo from Sihlwald station 30.5.1999 by Ilkka Siissalo.

A closeup of the Ce 4/4 no 41 'crocodile' locomotive.
Photo from Sihlwald station 30.5.1999 by Ilkka Siissalo.

A Sihltalbahn coach from the 1930´s, the X 351 is today a movable base for construction workers, but it´s still in surprisingly good shape. It gives a glimpse to the travelling on the Sihltalbahn in the pre-war times.
Photo from Sihlwald station 30.5.1999 by Ilkka Siissalo.

Very old SZU Sihltalbahn wagons, used as a base for track construction workers.
Photo from Sihlwald station 21.12.2001 by Ilkka Siissalo.

Motor draisine SZU Tm 10 is similar to those used by the federal railways SBB, but this one is a prototype of those used by SBB. SZU Sihltalbahn has a depot at Sihlwald and this draisine was for a long time used for moving wagons in and out of the depot halls. This motor draisine was built by the company Robert Aebi in 1949. It was later given or sold to the ZMB Zürcher Museums-Bahn.
Photo from Sihlwald station 21.12.2001 by Ilkka Siissalo.

More than 20 years later the small motor draisine is still there, at exactly the same track.
Photo from Sihlwald station 15.5.2023 by Ilkka Siissalo.

The historic Sihltalbahn wagons and locomotives shown above are being taken care of by the Zürcher Museums Bahn. This wagon acts as their storage house.
Photo from Sihlwald station 15.5.2023 by Ilkka Siissalo.