SBB Bm 2/2 (historical)

Updated: August 2026 – A very short, two-axle vehicle with no pantograph, moving a few wagons around: the SBB Bm 2/2 belongs to that class of small rail vehicles that were part of everyday life at every larger station for decades. Little has been written about them – but their designation tells you all the more. This page shows you how to read it.

What is the SBB Bm 2/2?

The SBB Bm 2/2 is a short, two-axle rail vehicle with an internal combustion engine. That’s all fully spelled out in the designation – you just need to be able to read it. Vehicles like this were procured for jobs where a large main-line locomotive would have been uneconomical: moving individual wagons, short transfer runs, service and construction duties, often on tracks with no overhead line. At the Swiss Federal Railways, they were therefore standard equipment at larger stations for decades.

Today, vehicles of this size are mostly preserved as historic stock. Where individual examples are located, whether they’re operational, and on what occasions they’re moved, changes constantly and can only be reliably confirmed with the relevant society or operator.

Bm 2/2, sign by sign

Sign	Meaning	What you can read from it
B	speed class	A is the fastest class, followed by B, C and D
m (lower-case)	internal combustion engine	exhaust and radiator area instead of a pantograph
2 (numerator)	powered axles	both axles transmit power
2 (denominator)	total axles	a very short vehicle with no bogies

The comparison makes the system tangible: an SBB Ee 3/3 is an electric shunting locomotive with three powered out of three axles – there, an e appears instead of an m. A vehicle like the SBB Am 843 also carries an m, but belongs to a different speed class. And the SBB Em 840 even combines several features at once in its designation.

The most important rule for Switzerland always stays the same: lower-case letters describe the traction. If the lower-case letter is missing entirely, the vehicle has no traction of its own – that’s the quickest way to recognise a driving trailer or carriage.

What two-axle diesel vehicles are for

Small shunting and service vehicles solve a simple problem: not every movement at a station needs a full-size locomotive. A single wagon that has to move from one track to another, a short train for construction work, a transfer within an area with no overhead line – a light, agile vehicle with its own engine is the right answer for that.

That’s precisely what produces the typical appearance: a short frame, few axles, a compact cab, no dependence on overhead wiring. And it’s also exactly why you can’t observe such vehicles in certain places – namely on operational railway land, which is fundamentally off-limits.

Independence from the overhead line is really the reason for the internal combustion engine. Workshop tracks, loading roads, siding connections and construction areas are often not wired; an electric vehicle simply couldn’t get there. A small diesel vehicle, on the other hand, can run wherever there are rails. That’s why this class has endured for decades – and why many examples are preserved today in heritage-society operation: they’re compact, technically manageable, and can be moved without overhead line.

How to recognise a Bm 2/2

The general order of steps for identification – from features visible from afar to fine detail – is explained in the guide to identifying classes.

Where you can even see historic small vehicles

Opportunity	Likelihood	Note
Announced society and museum events	high	By far the most reliable route
Heritage railways with public operation	medium to high	Check running days and vehicle deployment beforehand
Publicly accessible exhibition sites	medium	Vehicles here are usually static
Regular service on main lines	very low	Historic small vehicles don’t run there on a scheduled basis
Operational railway land, depots, storage sidings	irrelevant	No access – not a target for observation

Which societies exist in Switzerland and the German-speaking region, and how to get in touch with them, is covered in the overview of railway societies.

Photography and safety

Small vehicles are their own photographic challenge. They rarely stand in the open, are often obscured by wagons or structures, and can easily look lost in the frame from a standard perspective.

• Get closer than you would for a locomotive, but only within accessible areas – at events, that means the designated spaces.
• A low camera position makes short vehicles look sturdier rather than toy-like.
• Include the surroundings. With historic vehicles, the context is often the real information.
• Photograph the markings separately, because the designation and number on small vehicles are small and often poorly placed.

And the point that overrides everything else: tracks, operational railway land, shunting areas and storage sidings are off-limits. That applies to a rare historic vehicle just as much as to a regional train – the rules are summarised in the article on safe distance from the track.

Common mix-ups

Conclusion

The Bm 2/2 is a good example of how much you can say about a vehicle without a data sheet – as long as you master the Swiss system. Capital letter, lower-case letter and fraction give you speed class, type of traction and axle ratio. Anything beyond that is better asked of the relevant societies than taken second-hand.