Key takeaways
- ST43 means diesel plus freight: S for combustion engine, T for towarowa, 43 as the design number.
- No pantograph is the fastest way to rule out every electric class.
- A line locomotive, not a shunter: the letter T clearly separates it from the SM42 with its M.
- Its operational value lies wherever there is no overhead wire – on sidings, branch lines and in transhipment areas.
- Fleet numbers and operating areas change and depend on freight volumes, modernisation and operator structures.
Contents
Fact file
| Vehicle type | Diesel locomotive for freight traffic |
|---|---|
| Designation system | S = combustion engine, T = towarowa (freight traffic), 43 = design number |
| Traction principle | Combustion engine, no overhead wire required |
| Typical use | Freight trains, including on non-electrified sections; deployments vary |
| UIC country code | 51 for Poland |
Identifying features
Is this really the class in front of you?
- Markings reading ST43 with running number on the body
- No pantograph on the roof – the machine works independently of the overhead line
- Large line diesel locomotive with a long body, noticeably bulkier than the four-axle SM42
- As a rule ahead of freight trains, not passenger trains
- Exhaust system and radiator housings on the roof instead of electrical roof equipment
- UIC number with the country code 51 for Poland
Updated: August 2026 – The PKP ST43 is a line diesel locomotive for Polish freight traffic. Its code is typical of the Polish system: two letters are enough to fix traction and purpose. This page shows you how to read the code, how to tell a diesel locomotive from an electric one in seconds, and what freight traffic means for your spotting.
Spotted a diesel locomotive in freight traffic?
Freight sightings are rarely predictable – log them while you still have them in front of you.
What is the PKP ST43?
The ST43 is a diesel locomotive for freight traffic. Its name follows exactly the letter-and-number scheme of the Polskie Koleje Państwowe: S for a combustion engine, T for towarowa – freight traffic – and 43 as the design number.
That places it in the system at the same point as the electric PKP ET22, just with different traction. Both are intended for heavy trains; one needs overhead wire, the other does not. That is exactly where the diesel locomotive’s operational value comes from: it keeps working where the overhead line ends. Heavy freight traffic in Poland is mainly hauled today by PKP Cargo, one of Europe’s largest freight operators.
The S system: Poland’s diesel classes at a glance
The first letter fixes the traction, the second the purpose. Among diesel vehicles, that produces a manageable, clearly sorted family.
| Designation | Second letter | Purpose |
|---|---|---|
| SM42 | M – manewrowa | Shunting and trip working |
| SU42 | U – uniwersalna | Line service, including passenger trains |
| ST43 | T – towarowa | Heavy freight traffic |
| ST44 | T – towarowa | Heavy freight traffic, different design |
| ST46 | T – towarowa | Heavy freight traffic, imported design |
| SU45 | U – uniwersalna | Universal line service |
Anyone who has this table in mind can classify any Polish diesel locomotive before even knowing its design number. The number then provides the fine distinction within the group.
Roof first, then the letters
Pantograph or exhaust? That one observation decides between E and S and immediately halves the number of classes you need to consider. Only after that is it worth looking at the markings.
Identification in the field
Check the roof equipment
Exhaust systems, radiators and fan grilles instead of pantographs and insulators: that is a diesel locomotive, and so a leading S.
Assess the size
A long, bulky line machine points to T. A compact four-axle body points more towards the shunting class with M.
Look at the train
A long freight train fits the design. A passenger train would be unusual and a reason to check the identification again.
Read the marking and number
ST43 plus the running number completes the identification. Without the running number, the sighting remains incomplete.
Make freight traffic more predictable
Live reports from the community replace the missing timetable – and show you what is out there right now.
Spotting and photography
Freight diesel locomotives are a rewarding photographic subject: they work visibly, produce exhaust plumes when starting under load, and often run ahead of long, staggered trains.
- Photograph on a curve. Only there does the train become visible behind the locomotive. On a straight it disappears behind the front.
- Catch the start. The moment under load tells you more than a pass-through at constant speed.
- Watch the roof. Radiators and exhausts are part of a diesel locomotive’s visual language – a slightly raised viewpoint brings them into the picture.
- Keep the number legible. For classes without distinctive shape differences, the marking is the real information.
The basics for that are in the guide to taking good photos of trains, the choice of lens in the guide to focal length in train photography. How you even find freight workings using real-time data is covered in the article on tracking freight trains.
Operational railway land stays off limits
Track areas, shunting yards, sidings, transhipment terminals and stabling sidings are operational railway land and generally private property. Observing and photographing takes place exclusively from publicly accessible paths and platforms, with a clear distance from the track.
Documenting freight sightings properly
In passenger traffic, the timetable provides the framework: train number, line, time. In freight traffic, all of that is missing. It is all the more important to record the information you can actually observe.
Five details turn an observation into a usable data point: class designation, running number, date, location and – if identifiable – the operator. Anyone who also notes the train formation, whether it is a block train of uniform wagons or a mixed train, will recognise patterns at their own location after a few months.
Writing it down beats remembering
You mix up numbers faster than you think – especially when several similar machines pass on the same day. Recording it on the spot leaves no gaps in the archive later and nothing to reconstruct.
A second point concerns the images themselves. Photos of freight trains age differently from images of passenger traffic: wagon types, loads and operator liveries often disappear quietly. What looks mundane today will be documentarily valuable in ten years. That is exactly why it is worth photographing even the supposedly boring trains.
Third, a fixed routine helps: read the number first, then photograph, then note it down. On pass-throughs, this order decides whether the sighting is usable at all. At stationary trains in overtaking stations, on the other hand, you have time for all three steps – another reason to favour such locations.
Anyone who works this way builds up their own picture of freight traffic at their location over the years. That is more reliable than any list from the internet, because it rests on your own dated observations.
An additional note concerns the design numbers within the ST group. Several Polish diesel classes fulfil the same purpose and therefore carry the same pair of letters. They can only be told apart by the number – and by shape features that must be checked on the actual vehicle, not from memory.
That is why some healthy restraint pays off when identifying: better to note “ST class, number illegible” than to guess a design number. An honestly incomplete sighting remains usable, while a wrongly assigned one permanently corrupts your own archive.
Common mix-ups
It points to an ST43 if …
- no pantograph is present
- a large line diesel locomotive is running ahead of a freight train
- the marking reads ST43
- the UIC number carries country code 51
Look more closely if …
- you cannot read the design number – several ST classes fulfil the same purpose
- the machine is running for a private freight operator
- the vehicle has been modernised and deviates from the standard appearance
It is not an ST43 if …
- pantographs sit on the roof – then it is an electric locomotive like the ET22
- the marking begins with SM – then it is a shunting locomotive
- the typical Class 66 silhouette is visible – then the ST46 is more likely
Within the Polish diesel fleet, it is worth comparing it with the PKP ST44 (M62), which solves the same task from a different design school, and with the PKP SU45, whose U points to universal line service.
Verdict
The ST43 is not a vehicle you recognise by silhouette – it is one you classify by its code. Two letters fix traction and purpose, the design number the specific construction. Anyone who looks at the roof first and the marking second reliably reaches their goal with Polish diesel classes too.
Quick verdict
S for combustion engine, T for freight traffic, 43 for the design. No pantograph, large line machine, freight train on the hook – and the marking as confirmation.
Collect diesel classes systematically
Designation, number, location and date in one place – turning chance sightings into a real archive.
Summary
- The ST43 belongs to the line diesel locomotives of Polish freight traffic and is clearly classified by its code.
- Its name follows PKP logic: first letter for traction, second letter for use, then the design number.
- For identification, the missing roof equipment, the vehicle's size and the marking you read are enough.
- Because freight workings follow no published timetable, real-time data and patience are the most important tools.
Frequently asked questions
What does the designation ST43 mean?
In the Polish system, S stands for a combustion engine, meaning diesel traction, T for towarowa – freight traffic – and 43 is the design number. So the designation tells you what the vehicle runs on and what it was built for before you know any technical detail.
How do I tell ST43 and ET22 apart?
By the first letter and by the roof. S means combustion engine, E means electric. The ET22 carries a pantograph and depends on 3 kV DC, the ST43 does not. Both are intended for the same purpose – heavy freight trains – and so both carry the same T in second place.
What is the difference between ST43 and SM42?
The second letter and the size. T stands for heavy freight traffic on the line, M for shunting duty. The ST43 is accordingly the larger line machine, the SM42 the more compact shunting and trip locomotive. Both run on combustion engines and so both begin with S.
Why does an electrified network need freight diesel locomotives?
Because freight traffic rarely takes place entirely under overhead wire. Sidings, works railways, transhipment terminals and many branch lines have no overhead line. A diesel locomotive can haul the train right through without changing locomotives on the way – saving time and shunting effort at both ends of the transport chain.
How do I recognise a diesel locomotive from a distance?
By the roof. Electric locomotives carry pantographs, roof cabling and insulators. Diesel locomotives instead have exhaust systems, radiator housings and fan grilles. This difference is visible even in poor light and from a great distance and should always be the first identification step.
Does the ST43 also haul passenger trains?
That is not its design. The letter T points unambiguously to freight traffic. For passenger trains on non-electrified lines, the types with P or U are responsible in Poland, such as the SU classes. Exceptions occur in operation everywhere, but they are not the rule.
Where do you encounter the ST43?
On freight corridors, at transitions between electrified and non-electrified sections, and near industrial and transhipment sites. Which vehicles actually run there changes with freight volumes, operator structures and vehicle procurement – always check current information.
What belongs in a clean sighting?
Class designation, running number, date, location and, if possible, the operator. For freight trains, a note on the train formation is also worthwhile. Only this combination turns an observation into a data point you can later evaluate and compare with other sightings.
Log your sighting of the PKP ST43
Date, location and vehicle number logged in seconds – and visible to the community.
Related classes
PKP 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 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.
Electric locoPKP ET22
The ET22 is the heavy freight electric locomotive of the Polish network: six axles, two three-axle bogies, and a name that states its job directly.
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.
Diesel locoPKP SU46
The SU46 is a six-axle Polish universal diesel locomotive and looks confusingly similar to the SU45. Here's how to tell the two apart cleanly.
Who is behind it
Groups, brands, manufacturers and operators – who owns whom and how to recognise them out in the field.
Polskie Koleje Państwowe (PKP)
Polish locomotive designations are the most clear-cut numbering system in Central Europe: two letters tell you the traction and purpose before you've even read the number. The group structure behind them is considerably less clear – a lot of what's called PKP no longer belongs to it.
GroupPKP Cargo
PKP Cargo is the freight arm of the Polish state railway holding – and a special case: unlike most groups, the company runs trains itself while also holding stakes in subsidiaries at home and abroad. On the track you'll find one of Europe's oldest electric-locomotive fleets.
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