Key takeaways
- Em 840 is a self-explanatory name: E stands for shunting locomotive, m for internal combustion engine, 840 is the type number.
- Instead of a fraction like Re 4/4 II, modern Swiss vehicles carry a three-digit type number – here 840.
- Recognition method in the field: read the markings, observe the task, check the UIC number for country code 85.
- Shunting vehicles are working equipment: they move in areas that are off limits to observers – photograph them only from publicly accessible points.
- Locations of use change: where a particular machine is currently working shifts with operating concepts and timetable years.
Contents
Fact file
| Vehicle type | Shunting locomotive with internal combustion engine |
|---|---|
| Designation system | Swiss letter system: E = shunting locomotive, m = internal combustion engine |
| Type number | 840 – three-digit modern Swiss type number |
| Operator | SBB (Swiss Federal Railways) |
| UIC country code | 85 for Switzerland |
| Typical use | Shunting and trip-working duties; specific locations change over time |
Identifying features
Is this really the class in front of you?
- The Em 840 markings on the vehicle body – the capital E in the Swiss system stands for shunting locomotive
- No pantograph needed: thanks to its internal combustion engine, the machine also works in non-electrified track groups
- Shunting steps, grab handles and running boards at the vehicle ends – standard on shunting locomotives, unusual on main-line locomotives
- UIC number begins with the country code 85 for Switzerland
- Moves individual wagons or short groups of wagons rather than complete trains
Updated: August 2026 – The SBB Em 840 is a shunting locomotive, and its name already tells you that before you’ve even seen the vehicle. The Swiss designation system is one of the few in Europe that writes the task and the type of traction directly into the name. This page shows you how to read the code, how to place the machine in the field, and what applies when observing shunting vehicles.
Spotted a shunting locomotive? Note the number.
You rarely see shunting vehicles twice in the same spot – with Traintrack the sighting is logged in seconds.
What is the SBB Em 840?
The SBB Em 840 is a shunting locomotive with an internal combustion engine, operated by Swiss Federal Railways. The designation itself is the answer: the capital E stands, in the Swiss system, for shunting locomotive, the lower-case m for an internal combustion engine as the power source, and 840 is the type number of the modern three-digit system.
That also makes its operational role clear. Shunting locomotives don’t haul trains along the line; they move individual wagons and short groups of wagons: making up, delivering, collecting, transferring. Because it carries an internal combustion engine, the machine isn’t tied to the overhead line and can also work in non-electrified track groups and on siding tracks – the key difference from the electric shunting locomotive SBB Ee 922.
Reading the Swiss code: E, m and the number
No other European country reveals as much through its vehicle designation as Switzerland. Once you understand the system, you can say what you’re dealing with even for a completely unfamiliar vehicle.
Read the first capital letter
On main-line locomotives it stands for the speed class – A is the fastest group, followed by B, C and D. An E, on the other hand, doesn't mark a speed class but the task: shunting locomotive.
Check the lower-case letters
These describe the traction. An e stands for electric, an m for internal combustion engine. Ee thus becomes the electric shunting locomotive, Em the shunting locomotive with its own engine.
Place the number
Older vehicles carry a fraction such as 3/3 or 4/4: the numerator is the driven axles, the denominator the total axles. Newer procurements get a three-digit type number instead – here 840.
That’s exactly why two names sometimes turn up for the same machine: the classic SBB Re 420 (Re 4/4 II) carries both systems side by side. How to find and read such vehicle and train numbers in service in the first place is covered in the guide to decoding train numbers.
Memory aid for the lower-case letters
e for electric, m for motor. That's all you need for ninety per cent of all Swiss vehicle designations – the rest are special cases such as rack traction or service vehicles.
Where shunting locomotives turn up in Swiss operations
Shunting vehicles don’t follow the timetable, they follow freight volume. That makes them hard to plan for – and explains why most sightings happen along the way.
| Location | Chance of a sighting | What you’ll realistically see |
|---|---|---|
| Larger freight yards | high | Making up and breaking up wagon groups, often over hours |
| Stations with siding tracks | medium | Short trip workings to industrial customers, usually morning or evening |
| Pure passenger stations | low | Shunting vehicles turn up there at most for wagon transfers |
| Works areas and depots | not accessible | Private premises – visible from outside at best |
| Stabling groups at the edge of a station | medium | Machines standing between duties, often clearly visible |
Locations of use change
Which stations are served with which vehicles depends on operating concepts, customer connections and timetable years. Older lists from the internet go out of date especially fast for shunting vehicles – check the situation on site or via current community sightings.
See what's being reported right now
Live sightings from the community show you which vehicles are currently out and about – before you set off.
Photographing shunting locomotives: harder than it looks
A shunting locomotive stands still, moves slowly, and so seems like an easy subject. In practice it’s one of the most thankless vehicles of all: it usually stands in the middle of the track field, half hidden by wagons, often against the light.
Find a spot from the end of the platform
The end of a publicly accessible platform is often the only legal point with a clear view into the track field. You don't go any further than that – tracks and shunting areas are operational railway land and off limits.
Plan for a telephoto focal length
Shunting vehicles are rarely close. Without a decent focal length, all that's left of the vehicle in the frame is a speck – the distance isn't negotiable here, so the lens has to deliver.
Focus on the markings
The real information is the lettering on the vehicle body. Frame the shot so that the designation, and ideally the UIC number too, stays legible.
Wait for movement
A shunting machine with wagons attached tells a bigger story than a static shot against a grey backdrop. Patience beats any amount of technique here.
Which focal length makes sense for this is covered in the guide to focal length in train photography; the basic technique is in the guide to good photos of trains. If you’re specifically out and about in freight traffic, the article on tracking freight trains helps too.
One point is often underestimated: shunting vehicles are the vehicle group with the lowest documentation density of all. Main-line locomotives and multiple units get photographed thousands of times over because they run to a timetable and are easily accessible. Shunting locomotives, by contrast, work off to one side, often without an audience, and usually disappear unnoticed at the end of their service life.
For you that means: a clean sighting with markings, the full UIC number, date and location is worth more for these vehicles than the umpteenth photo of a well-known main-line locomotive. Anyone who keeps consistent notes over the years ends up with data that hardly anyone else has – and can trace afterwards which machines worked where and when.
The same logic applies to the electric relative: the SBB Ee 3/3 represents the classic generation of Swiss shunting locomotives, whose fraction-based designation already feels historic today.
Common mix-ups and how to rule them out
It points to an Em if …
- the markings begin with Em
- the vehicle works on non-electrified track
- it moves individual wagons rather than whole trains
- the UIC number carries the country code 85
Look more closely if …
- you can't read the markings from a distance
- the vehicle is stabled between other machines
- it belongs to a private railway or industrial operator
It's not an Em if …
- the markings begin with Ee – that's an electric shunting locomotive
- a Re, Am or Bm comes first
- the vehicle is hauling a complete train along the line
Operationally, the closest relative to the Em 840 is the diesel-powered SBB Am 843 – there, however, the capital A points to a main-line locomotive of the fastest class, not a pure shunting vehicle.
Conclusion
The Em 840 isn’t a vehicle you’d plan a day trip around – but it’s a very good teaching example. It illustrates the entire Swiss designation system in one go: task, traction, vehicle generation, all in five characters. Once you understand it, you’ll read every Swiss locomotive designation afterwards without needing to look anything up.
In short
E stands for shunting locomotive, m for internal combustion engine, 840 for the type. The machine is mostly spotted in passing at the edge of freight yards – and photographed only from publicly accessible locations.
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Summary
- The Em 840 belongs to the group of Swiss shunting vehicles with thermal traction and can be identified unambiguously from its markings.
- The Swiss designation system provides more information than a plain serial number – it describes the vehicle's task and traction.
- For spotters, the machine is a fringe vehicle in the best sense: rarely sought out deliberately, but often spotted along the way.
- Anyone documenting it notes the markings, the full UIC number, the date and the location – the rest follows from there.
Frequently asked questions
What does the designation Em 840 mean?
The capital E marks a shunting locomotive in the Swiss system, the lower-case m an internal combustion engine as the source of traction. The number 840 is the type number of the modern three-digit system. Read together, Em 840 means: shunting locomotive with internal combustion engine, type 840, operated by SBB.
Why doesn't the Em 840 carry a fraction like Re 4/4 II?
Older Swiss vehicles carry a fraction that sets driven axles against total axles – for example Ee 3/3 for three driven axles out of three. For more recent procurements, SBB switched to three-digit type numbers. Both systems exist side by side, which is why you'll see Re 420 and Re 4/4 II used for the same vehicle in service.
Where do you see shunting locomotives like the Em 840?
At freight yards, on siding tracks, in stabling areas and around works – wherever wagons are moved individually. From a public platform you'll usually see them at the edge of the track field. Which locations are currently served changes with operating concepts and can't be pinned down for good.
Is the Em 840 a diesel locomotive or a hybrid locomotive?
The lower-case m in the designation only tells you that an internal combustion engine is on board. Whether a machine also carries an energy store or a second power source can't be read from the code alone. That detail belongs to the individual vehicle and its markings, not to the type designation.
How do I tell the Em 840 apart from the Ee 922?
By the second lower-case letter: Ee means electric shunting locomotive, Em shunting locomotive with internal combustion engine. An Ee therefore depends on overhead line and carries a pantograph, while an Em can also work on non-electrified track. When in doubt, the designation marked on the vehicle settles it.
Am I allowed to photograph shunting vehicles?
Photographing from a publicly accessible platform or from the street is generally unproblematic. Track areas, shunting yards, depots and stabling groups, on the other hand, are operational railway land and off limits – even where there's no fence in the way. The legal details depend on the individual case and the operator's house rules.
How many machines of the Em 840 class are there?
Reliable, permanently valid fleet figures are hard to give for shunting vehicles: they get rebuilt, renumbered, sold and withdrawn without this being documented widely in public. Your own observation is more reliable – every number you note down is a data point you can evaluate later.
Does the UIC number of Swiss vehicles always begin with 85?
The country code 85 stands for Switzerland and appears at a fixed position in the twelve-digit UIC number. The two digits before it describe the vehicle type – for railway service vehicles, for instance, 99. So the number alone already tells you which country a vehicle comes from and which group it falls into.
Log your sighting of the SBB Em 840
Date, location and vehicle number logged in seconds – and visible to the community.
Related classes
SBB Ee 922
The Ee 922 is a modern electric shunting locomotive of the SBB. Its three-digit number shows how the Swiss classification system has changed – here's how to read both.
Diesel locoSBB Am 843
The Am 843 is the SBB's four-axle diesel locomotive for shunting, engineering and main-line duty. This page explains the designation and the recognition features.
Electric shunterSBB Ee 3/3
The Ee 3/3 is the classic electric shunting locomotive of the SBB: three powered out of three axles. Here's how to read the designation and identify it reliably.
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