Key takeaways
- SU46 means diesel universal locomotive, design 46: S for combustion engine, U for universal duty.
- Fastest route to identification: six axles, full-width body, no pantograph – then read the number.
- The biggest source of error is confusion with the SU45; both belong to the same vehicle family and look very alike.
- Its territory is non-electrified lines – wherever overhead wire hangs in Poland, electric locomotives and multiple units work instead.
- Fleet and deployment are changeable and shift with electrification and vehicle procurement.
Contents
Fact file
| Vehicle type | Six-axle diesel-electric line locomotive for universal duty |
|---|---|
| Origin | Polish design from the generation of large line diesels |
| Wheel arrangement | Co'Co' – two three-axle bogies |
| Body design | Full-width body with a cab at each end |
| Designation | S = combustion engine, U = universal duty, 46 = design number |
| UIC country code | 51 for Poland |
Identifying features
Is this really the class in front of you?
- Six axles on two three-axle bogies
- Body over the entire vehicle length, no separate bonnet
- A cab at each end of the vehicle with large front windows
- No pantograph – the roof shows radiators and exhausts instead
- Vehicle number begins with the code SU46
- Very similar proportions to the SU45 – the markings decide
Updated: August 2026 – Six axles, a continuous body and no pantograph: the SU46 belongs to the generation of large Polish line diesels and is one of those vehicles where a first glance isn’t enough. This page shows you how to identify it, what its code says, and how to cleanly separate it from its sister design, the SU45.
With similar designs, the number counts
Log the code, number and location on the spot – in Traintrack it takes less than half a minute.
What is the PKP SU46?
The SU46 is a six-axle diesel-electric line locomotive for universal duty, built in Poland for work on lines without overhead wire. It has a full-width body over the entire vehicle length and a cab at each end.
The code here is no mere label but a statement: S for combustion engine, U for universal duty, 46 for the design. In Germany you would need to know what’s behind a three-digit number – in Poland you read it off directly. That is exactly why it’s worth learning the system properly once, rather than memorising individual classes. The code system of the Polskie Koleje Państwowe turns two letters into a complete statement about traction and purpose.
The Polish designation system as a tool
| Character | Meaning | Examples |
|---|---|---|
| First letter | Traction type | E = electric, S = combustion engine |
| Second letter | Use | U = universal, P = passenger train, T = freight train, M = shunting duty, N = railcar |
| Number | Design number | 46 for the SU46, 45 for the SU45, 22 for the ET22 |
The table carries further than you might first think. The ST44 is the freight diesel locomotive, the ST43 another heavy diesel design for transport duty, and the electric ET22 takes on the same task under overhead wire. On top of that, every vehicle carries a twelve-digit international number with country code 51 for Poland; how this number is structured and what the check digit does is explained in the article on the UIC number on the vehicle.
Which Polish diesel locomotive is that?
Quick identification: diesel locomotive in Poland
Heavy box-body diesel locomotive, such as the SU45 or SU46
Six axles and a full-width body point to this vehicle family. Only the markings clarify which of the two designs it is.
Diesel locomotive with a central bonnet, such as the ST44
The narrow machine bonnet between two cabs is typical of this body shape. The SU46 looks different.
Smaller shunting or branch-line locomotive
Four axles and a short body point to the common shunting design. An SU46 is noticeably larger.
Not a diesel locomotive
With a pantograph, the code in the Polish system begins with E. That rules out every S design.
Working systematically rather than by intuition pays off especially well with these vehicles. How to work through features in the right order is described in the guide to identifying classes.
Operational classification and search strategy
| Environment | Chance of a sighting | Why |
|---|---|---|
| Non-electrified main lines | high | Core territory of heavy line diesels |
| Stations at the transition to electrification | medium | Traction changes and dwell times |
| Special, diversionary and replacement services | medium | Scheduled at short notice, hardly plannable |
| Fully electrified main routes | low | Electric locomotives and multiple units dominate there |
| Purely urban local-transport hubs | very low | No deployment area for this vehicle class |
Everything operational is on the move
Deployment areas, keepers and fleets of this vehicle generation change with electrification projects, tenders and new procurements. Treat any older fleet statement as a snapshot and check the current status.
Who last reported an SU46?
Real-time community sightings are the most realistic basis for planning your next trip.
Spotting and photo tips
Two photos instead of one
Always take a photo of the vehicle number after the main shot. With the SU45 and SU46, that's not perfectionism – it's the only way to identify your sighting beyond doubt later on.
The same rules apply for composing the image as for any large box-body locomotive: a three-quarter view of around 30 to 45 degrees gives the surface depth, flat morning or afternoon light picks out edges, and a slightly raised viewpoint separates the vehicle from the background. The choice of location still matters: platforms, public paths and bridges yes – track areas, depots and stabling sidings no, without exception and without discussion.
One point that matters especially for this vehicle class: large diesel locomotives often stand around longer than you’d think. Unlike a multiple unit that departs again after two minutes, line locomotives wait for a traction change, train formation or crew change. That gives you time to change your viewpoint, check the background and produce a considered image instead of a hasty snapshot. Use this time to read the full markings cleanly as well.
Conversely, once the locomotive is moving, you only get one attempt. Set exposure and focus in advance, decide on a framing beforehand, and don’t hold the shutter release back until the last second. A slightly early shot can be cropped – a late one only shows the wagons.
Location before shot
No shot justifies stepping onto the track, bypassing barriers or using operational railway land. If an image only works from an impermissible vantage point, the image is the wrong idea – not the rule.
Because many good vantage points at stations are far from the subject, focal length is often more decisive here than the camera itself. Which lenses are suited to this purpose and where cheap telephoto lenses hit their limits is covered in the guide to the best telephoto lens for railway photography. For evaluating your photos and notes afterwards, a cleanly kept sighting log helps.
Common mix-ups
It points to the SU46 if …
- you count six axles on two three-axle bogies
- the body is full-width over the entire length
- no pantograph is present
- SU46 is explicitly on the vehicle
Look more closely if …
- shape and size fit but the number is illegible – then the SU45 is also a possibility
- an unfamiliar livery obscures the lines
- you only see the vehicle against the light or from behind
It is not an SU46 if …
- a narrow machine bonnet lies between the cabs
- you only count four axles
- a pantograph sits on the roof
Verdict
The SU46 is a vehicle for people who look closely. Axle count and body shape put you in the right vehicle class, but only the markings separate it from the SU45. Anyone who gets into the habit of documenting every sighting with the full number has the decisive advantage with this design.
Quick verdict
Six axles, full-width body, no pantograph, code SU46: those are the four points. The first three put you in the right family, the fourth makes the sighting unambiguous.
Collect Polish designs systematically
With number, date and location in one app, you see straight away which codes you're still missing.
Summary
- The SU46 is a heavy Polish diesel locomotive for mixed duties on lines without overhead wire.
- Its code follows the PKP scheme of a traction letter, a use letter and a design number.
- Visually it is barely distinguishable from the SU45 – the vehicle number is therefore a mandatory part of every sighting.
- Anyone looking for it specifically orients themselves on non-electrified main lines and on current sighting reports.
Frequently asked questions
What does the designation SU46 mean?
The Polish system encodes traction and purpose in two letters. S stands for a combustion engine, U for universal duty, meaning use ahead of both passenger and freight trains. The 46 is the design number. From the code you can immediately tell it's a versatile diesel locomotive.
How do I tell the SU46 and SU45 apart?
Via the markings. Both are six-axle diesel locomotives with a full-width body and the same basic idea, so the overall impression from a distance barely helps. Photograph the vehicle number separately too – that's the only truly reliable distinction in the field.
How many axles does the SU46 have?
Six, in the wheel arrangement Co'Co'. That places it in the class of heavy line diesels and clearly sets it apart from four-axle shunting and branch-line locomotives such as the SM42.
Does the SU46 have a pantograph?
No. The first letter S rules that out – it denotes combustion traction in the Polish system. If you see a pantograph on the roof, the designation begins with E, as with the EU07 or the ET22.
Where can I encounter the SU46?
On non-electrified lines and in diagrams that run through both electrified and non-electrified sections. Exactly where depends on traffic contracts and the state of electrification and changes with every timetable year. Current sightings are more reliable here than any list.
Does the SU46 also run to Germany?
Cross-border deployments depend on approvals and specific services, not on the electrification system – diesel locomotives are independent of that. Whether Polish line diesels actually turn up at a particular crossing along the Oder and Neisse should be checked via current reports rather than assumed.
How do I identify the individual machine?
By the full vehicle number on the vehicle. In addition, every vehicle carries a twelve-digit UIC number, in which 51 is the country code for Poland. Number plus date plus location together produce a sighting that remains usable even years later.
Is the SU46 suitable for passenger trains?
The letter U explicitly stands for universal duty, meaning both. Pure freight locomotives carry a T in the Polish system, pure passenger locomotives a P – a system that writes the purpose directly into the designation.
Log your sighting of the PKP SU46
Date, location and vehicle number logged in seconds – and visible to the community.
Related classes
PKP SU45
The SU45 is a six-axle Polish universal diesel locomotive. Its code reveals both traction and purpose – and three features are enough for a confident ID.
Diesel locoPKP ST44 (M62)
The ST44 is Poland's version of the Soviet M62 – six axles, loud and unmistakable. Here's how to read the code and recognise the locomotive in the field.
Diesel locoPKP ST43
The ST43 is a line diesel locomotive for Polish freight traffic. Its code names both traction and purpose – and sets it clearly apart from shunting and electric classes.
Diesel locoPKP Cargo ST46 (Class 66)
The ST46 is the Polish designation for the EMD Class 66 – a six-axle diesel locomotive whose shape is unmistakable right across Europe.
Diesel locoPKP SM42 / SU42
The SM42 is Poland's classic diesel shunting locomotive, nicknamed Tamara. As the SU42, the same class takes on passenger duties – one letter makes the difference.
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