Operation in scheduled services began in October 1978, the sets were manufactured by Simmering-Graz-Pauker in Graz.

After the first test runs in October 1978, the railcars were used for the first time in scheduled service on the later S80 line from December 1978.

After test runs in Tyrol, they were used for the first time on the main line from spring 1979, primarily in the direction of Stockerau.

However, the problems with the compressed air supply could only be permanently eliminated with the use of heavy piston compressors from unit 4020.81 onwards.

[1] With the reopening of the Suburban line in 1987, railcars 4020 095 to 100 were equipped with a door area monitoring system with light barriers for unaccompanied operation.

[2] In the years from 1993, all railcars underwent a major overhaul, which was recognisable both technically and externally by the change of paintwork.

From 2002, the railcars that had already been rebuilt at this time were fitted with an emergency brake override (EBO), while the others received them during the subsequent main upgrade.

The passenger compartment in the railcars is ventilated via air ducts in conjunction with the intake from the machine fans.

[3] The original plan was to convert the toilets to a closed system as part of the main upgrade.

However, when the toilet's were moved to the end of the intermediate coach on the railcar side, only the conversion was prepared on most trains.

Many details of the units were modernized as part of the main improvements carried out from 1993 onwards: The roller conveyor displays for destination indication with their characteristic blue lettering on a white background were replaced by matrix displays.

From then on, the seat covers were patterned blue/purple, the previously blood-orange door areas and the brown luggage racks and dung bins were traffic lane purple.

From 2004, units 4020 281, 283, 294, 296, 297, 299, 300 and 310 to 320 were also repainted in the red/grey diagonal design intended by ÖBB for local transport at that time, which also involved a change to the interior in gray/blue (instead of purple) and new lettering and pictograms.

(ivory, gray-white and diagonal design) From the end of 2002, all sets were also equipped with an emergency brake override (Nahverkehrs-NBÜ) and reclassified as series 4020.2 (the order numbers were raised by 200).

In order to minimize maintenance costs on the one hand and improve visibility for the driver on the other, the trains were equipped with LED headlights between 2014 and 2015.

To increase safety, the intermediate carriage of the 4020 310 (7020 310) set was converted in 2023 and fitted with interior and exterior cameras on a trial basis.

In September 2023, unit 4020 242 was converted into a disco train to mark the 100th anniversary of the ÖBB company.

The frames of the running bogies are designed as open H-frames; a tractive force link is used for power transmission.

The air bellows absorb all longitudinal and transverse forces and ensure a constant floor height regardless of the load on the carriages.

If this fails, the pressure in the main air line is immediately reduced accordingly, but the electrodynamic brake is then suppressed due to the risk of overbraking.

Since the main upgrade, all wheelsets have had axle-selective (previously bogie-selective) electronic wheelslip control.

Each railcar is equipped with a contactless thyristor control system; the braking and tractive force is infinitely variable.

Thanks to this and other innovations such as automatic travel and brake control (AFB) with automatic start-up, the locomotive driver can devote more time to observing the route and his work is made easier compared to older vehicle control systems.

Conventional switching operations are avoided, the power converter consists of an extinguished and an unextinguished bridge.

The traction motors are housed in the bogie frame in a tatz bearing design and are supported by rubber layer springs.

The planning, which previously only comprised nine circulation days and was concentrated on a few lines, which resulted in a rather high proportion of unscheduled operations, was abandoned.

The new timetable requires 28 trainsets daily and includes almost all rapid transit lines whose vehicles are provided from Floridsdorf.

Shortly before the timetable change in December 2021, unit 4020 273 was withdrawn after the 130th railcar of series 4746 had been approved for passenger service.

In April 2023, numerous sets parked in Vienna-Jedlersdorf and Floridsdorf were transferred to Romania for scrapping.

The first Class 4020 was painted with graffiti in November 1989 at Floridsdorf, but it is unclear if the train subsequently went into service before being cleaned.