Stadler KISS (Class 445 / 446)

Updated: August 2026 – Double-deck, no locomotive change, one continuous multiple unit: the Stadler KISS is one of the vehicles that shape regional services on high-demand routes. This page shows you how to recognise it, why the class number is, for once, not enough as the sole feature here, and how to tell it apart from the rival double-deck designs.

What is the Stadler KISS?

The KISS is an electric double-deck multiple unit from Stadler. The name stands for Komfortabler Innovativer Spurtstarker S-Bahn-Zug (comfortable, innovative, fast-accelerating suburban train) and – like FLIRT – denotes a product family, not a single class. Outside Germany, KISS units run as, for example, Class 2300 of CFL. In Germany, the vehicles run under numbers from the 445 / 446 block. The largest operator there is Ostdeutsche Eisenbahn.

Conceptually, the KISS solves a specific task: lots of capacity on lines with closely spaced stops and high demand, without the time lost with a locomotive-hauled push-pull set. The drive is distributed across the unit and there’s no separate locomotive – which gives the train strong acceleration, something the “Spurtstark” (fast-accelerating) in its name also alludes to.

The construction test: count the bogies

The most important difference between Stadler’s two big families lies underneath the vehicle.

Feature	KISS	FLIRT
Car profile	double-deck	single-deck
Bogies	two per car	one per gangway (Jacobs type)
Car formation	conventionally coupled cars	continuous articulated train
German classes	445 / 446	427, 428, 429 and extensions
Typical use	high-demand regional express routes	regional and regional express services

Once you’ve taken that in, you’ll place multiple units very quickly. The Stadler FLIRT is the opposite pole: there, one more bogie than car sections; here, two bogies per car.

Paired classes: why 445 and 446 belong together

The German class scheme numbers the parts of a unit separately. The end car with the driving cab gets one number, the matching intermediate car another. You’ll find the same principle on Class 423 / 433 and many other multiple units.

In practice, that means:

• One unit carries several class numbers. That’s not a lettering error, it’s the system.
• The train is still a fixed unit. The cars aren’t swapped individually in service.
• When you take notes, include the end car’s number. It’s the usual reference point for a sighting.

Exactly where these numbers are lettered on the vehicle, and how to read them quickly in service, is explained in the article on finding train and vehicle numbers.

Why double-deck – and why as a multiple unit

Double-deck vehicles in German regional services aren’t a fashion, but an answer to a capacity problem: platforms are only so long. If a train can’t get any longer, the only way is up.

The price is well known: double-deck cars need more time for passengers to board and alight, because travellers have to use stairs. That’s why the doors sit in the lowered middle section between the bogies – there, the way to both decks is shortest and the entrance is closer to platform height.

The second decision is the one between push-pull train and multiple unit:

• Locomotive-hauled push-pull train. A locomotive at one end, a driving trailer at the other. Flexible, because the locomotive and coaches can be diagrammed separately – but heavier, slower to accelerate and with the drive concentrated at a single point.
• Multiple unit. The drive is distributed across the unit, and all powered axles pull together. The result is better acceleration, more even axle loads and a shorter train for the same capacity.

On lines with closely spaced stops, acceleration counts for more than top speed – every second spent pulling away is lost again at every stop. That’s exactly what the design of a vehicle like the KISS is aimed at.

For identification in the field, the difference is trivial to check and yet the most important step: look at the front of the train. If there’s a separate locomotive there, it’s a push-pull train like the DB Regio Dosto. If the leading car is itself part of the unit, you’re looking at a multiple unit.

Where and how to photograph double-deck multiple units

Which focal length makes sense for long multiple units is covered in the guide to the best telephoto lens for railway photography. Suitable locations with long platforms and a view into the distance are collected in the overview of the best stations for trainspotting.

Common mix-ups

The three realistic candidates are all double-deck – and that’s exactly what makes them tricky.

• Class 445 / 446 (Twindexx Express): the same numbers, a different design. Here the class number doesn’t help; the shape of the front end, the door layout and the operator decide.
• DB Regio Dosto (Twindexx Vario): not a multiple unit, but a locomotive-hauled push-pull train. A look at the front of the train settles it immediately.
• Stadler FLIRT: the same manufacturer, but single-deck and built as an articulated train.

Conclusion

The KISS is a good example of the fact that German class numbers don’t always point unambiguously to one design. Anyone who relies on the number alone will quickly end up with the wrong design in the 445 / 446 block. What’s reliable instead are the construction features: double-deck, no locomotive, two bogies per car – and, as confirmation, the full twelve-digit vehicle number.