When the industrial revolution in Switzerland started in earnest, tens of small private railroads were built as connection lines from "big" railroad´s stations up small river valleys and to connect more distant villages to the main train lines. One of them, BD, Bremgarten-Dietikon line was opened 1. July 1876 as a narrow gauge local line to connect the marvelously beautiful medieval town of Bremgarten to the main SBB line between Basel and Zürich at Dietikon station. This was the beginning of the train company BD, Bremgarten-Dietikon Bahn. Another small railroad, but this time of normal gauge, connected Wohlen and Meisterschwanden. This company, WM or Wohlen-Meisterschwanden Bahn started cooperation with BD. A third rail was installed on the WM track so that narrow gauge trains could run all the way through and finally in the year 2000 these two companies were fusioned into what became the BDWM Transport AG. Finally the normal gauge third rail was dismantled and all that remained was the narrow gauge line.

Then in 2018 another fusion took place as BDWM Transport and the narrow gauge rail company Wynen- und Suhrentalbahn WSB fusioned into what is now called Aargau Verkehr AG AVA. WSB operated a narrow gauge line from Schöftland to the larger city of Aarau and further on to Menzigen. In 2019 Aargau Verkehr AVA operates one metre gauge line from Dietikon via Bremgarten to Wohlen, and this is the line S17 of the Zürich area S-Bahn system, then the Aarau–Menziken and Aarau–Schöftland lines of the former Wynental- und Suhrentalbahn (WSB) as line S14 of S-Bahn Aargau and finally also a new S-Bahn line called Limmattalbahn from Zürich-Altstätten to Schlieren, which is to be continued to Killwangen-Spreitenbach in 2023.

This train is of the type that Aargau Verkehr uses at the time as this text was being written in 2019. These are of the type ABe 4/8 built by Stadler. There are 14 of these units and they are called "Diamant" or diamond. The colours shown on this picture are still from the times of BDWM Transport AG. In 2019 these trains are now gradually all getting a new livery by new tapings with a prominent new AVA logo at their fronts.
Picture from Wohlen station 27.9.2017 by Ilkka Siissalo.

A closeup of the same Stadler ABe 4/8 Diamant no.5009 as above.
Picture from Wohlen station 27.9.2017 by Ilkka Siissalo.

Still the same Stadler ABe 4/8 Diamant no.5009 as above. These new trains are very tram-like.
Picture from Wohlen station 27.9.2017 by Ilkka Siissalo.

This picture is from 2003, when the BD and WM were still separate entities but were running with similar tram-like trains taken in use in the late 1990s. BD's trains were orange and ran on the Dietikon to Bremgarten line and WM's similar trains were dark blue and started also at Dietikon and ran via Bremgarten, but continued on to Wohlen. The trains and the track are very tram-like. Operating voltage is 1200V DC.
This is one of the that time WM's then very modern trains of the type Be 4/8 photographed at the Dietikon station 2.12.2003 by Ilkka Siissalo.

These class BDe 8/8 three-part articulated light rail wagons were the ones that operated on BD's route before the Be 4/8 wagons shown above. These were built in 1969 by Schweizerische Wagon- und Aufzugfabrik (SWS) and Maschinenfabrik Oerlikon and there were originally nine units built. They were all taken out of regular use in 2012 and even as this picture was taken in 2003, they were used only as rush-hour additional trains on the S17 line from Dietikon to Bremgarten. These trains consisted of three motorised pieces, each with four axles, so the trains had 8 motors with a total power rating of 588 kW and a top speed of 70 km/h.
Picture from Dietikon station 2.12.2003 by Ilkka Siissalo.

The same two BDe 8/8 wagons as above, now just leaving Dietikon towards Bremgarten.
Picture from Dietikon station 2.12.2003 by Ilkka Siissalo.

Wynental- und Suhrentalbahn WSB used to operate using exactly the same tram-trains as BD and WM at the time. This picture is from 2002 and the lady in the picture is train photographer Sanna Siissalo.
Picture from Schöftland station 1.9.2002 by Ilkka Siissalo.

Side view of the same WSB train as above. These Be 4/8 trains were practically identical with the ones used by BD and WM. Note how the train uses both pantographs at the same time. This is due to the very low operating voltage of only 750 V DC. This train is from the year 1992. Note that the BDWM line operates at 1200 V DC.
Picture from Schöftland station 1.9.2002 by Ilkka Siissalo.

Still the same train as above, ready to leave from Schöftland towards Aarau. This is the Suhrental line.
Picture from Schöftland station 1.9.2002 by Ilkka Siissalo.

Even older trains of the Wynen- and Suhrentalbahn WSB, these Be 4/4 trains date back to 1965 and 1979. The picture quality is unfortunately not very good as it was taken through a rather icy and dirty depot garage window.
Picture from Schöftland 1.9.2002 by Ilkka Siissalo.