PKP Cargo ST46 (Class 66)

Updated: August 2026 – The PKP Cargo ST46 is the Polish version of the EMD Class 66 – a six-axle freight diesel locomotive whose silhouette is the same all across Europe. Once you’ve seen it once, you’ll recognise it anywhere. This page explains what the code ST46 means, how to identify the type, and how to make freight workings predictable at all.

What is the PKP Cargo ST46?

The ST46 is a six-axle diesel locomotive for heavy freight services, built by EMD and part of the widespread Class 66 family. The Polish designation follows the usual scheme: S for a combustion engine, T for towarowa – freight – and 46 as the type number.

That makes it the diesel counterpart to the electric PKP ET22: the same job, the same number of axles, an entirely different type of traction. That’s exactly where its operational value lies – a diesel locomotive can haul a train where there’s no overhead line at all, for example on sidings and in transhipment areas.

The Class 66 shape: identified in a second

Few European locomotives are this easy to identify. The basic shape is practically identical across all countries and operators.

Diesel in freight service: why the ST46 exists at all

At first glance, a diesel locomotive on a well-electrified network looks superfluous. In practice, it isn’t – for entirely operational reasons.

Situation	Electric locomotive	Diesel locomotive
Continuous main line under overhead wire	ideal	possible, but uneconomical
Siding with no overhead line	not possible	ideal
Transhipment terminal and works railway	usually not possible	the standard case
Train reaching the customer with no locomotive change	rarely possible	exactly the advantage
Engineering works with the overhead line switched off	not possible	usable

The ST46’s reason for existing therefore sits at the start and end of the transport chain, not out on the open line. How to make freight workings tangible with real-time data is shown in the guide to tracking freight trains.

Spotting and photography

The Class 66 is a rewarding but idiosyncratic subject. The body is long and low, and the cab sits at one end – so front-on shots quickly look squat.

• Choose a three-quarter view. An angle of 30 to 45 degrees shows the cab and the length of the body together and brings out the typical proportions.
• Include the train. With heavy block trains, the train is part of the story. On a curve it fans out behind the locomotive and becomes visible.
• Watch for exhaust plumes. When starting under load, the smoke can become a subject in its own right – but only if the light and background cooperate.
• Keep the marking in shot. Without a legible number, a Class 66 photo can hardly be assigned to a country later.

The basics for this are in the guide to good photos of trains, and lens choice is in the guide to focal length in train photography.

The UIC number as a second layer of certainty

When the same type runs in several countries, the class designation alone isn’t always enough. The twelve-digit UIC number then provides the extra layer that makes a sighting unambiguous.

It’s lettered on every vehicle in European service and contains several blocks of information: a marker for the vehicle type, the country code, a vehicle number and a check digit. For Poland, the country code is 51. On railway service vehicles you’ll find 99 in the first two digits, and other codes on traction vehicles.

For documentation, that means concretely: photograph the side wall so that the class designation and the UIC number both fall within the frame. For a locomotive that exists in near-identical form in half a dozen countries, that’s the difference between usable evidence and a nice picture that says nothing.

A second point concerns train formation. Class 66 machines at PKP Cargo often run ahead of block trains – trains made up of uniform wagons shuttling between two points. For spotters, that’s useful information: anyone who’s seen such a train once at a location has a good chance of finding it there again. Still, don’t rely on fixed times – block train services follow contracts and volumes, not a timetable booklet, and both change.

Anyone who collects such observations over months builds up their own solid picture of freight traffic at their location. That’s considerably more reliable than any list from the internet, because it’s based on their own data.

Common mix-ups

For a comparison within the Polish diesel fleet, it’s worth looking at the PKP ST43 and the PKP ST44 (M62) – both carry the same ST for diesel-powered freight, but come from entirely different design schools.

Conclusion

The ST46 is a textbook example of how internationally built series locomotives get slotted into national designation systems. You’ll recognise the shape anywhere; the code tells you it belongs to Poland. For identification, a glance at the roof and the silhouette is enough – the rest is documentation.