Class 231

Updated: August 2026 – Six axles, a tall angular body and a deep, even rumble: the Class 231, carried by the Deutsche Reichsbahn as Class 131, belongs to the family of main-line diesel locomotives imported from the Soviet Union. Within this family it stands for a clear specialisation – freight traffic without train heating. This page places it technically, historically and operationally.

What is the Class 231?

The Class 231 is a six-axle diesel-electric freight locomotive of Soviet production, which the Deutsche Reichsbahn procured in the early 1970s and classified as Class 131. Its wheel arrangement is Co’Co’, and it has no train heating.

That gives it a clearly defined job: heavy freight trains on non-electrified main lines. The closely related sister class fitted with electric train heating is the Class 232, which as a general-purpose locomotive stayed in service considerably longer. This family later also produced the Class 241, strengthened for heavy freight traffic.

Hydraulic or electric: the two German traction philosophies

Anyone wanting to identify German diesel locomotives needs to know this dividing line, because it runs almost exactly between the fleets of the two former state railways.

Feature	Bundesbahn designs	Reichsbahn import locomotives
Transmission	diesel-hydraulic via torque converter	diesel-electric via generator and traction motors
Typical wheel arrangement	B’B’ (four axles)	Co’Co’ (six axles)
Typical examples	216, 218, 225	231, 232, 241
Starting behaviour	engine revs audibly, speed follows with a delay	smoother, stepped power build-up
Body shape	enclosed body, medium length	tall angular body, large ventilation grilles

This table is surprisingly useful in the field: axle count and sound alone can put you in the right family before you even read the number. The four-axle hydraulic main-line locomotives of the Bundesbahn, such as the Class 218, look completely different from the six-axle import machines of the Reichsbahn.

How to identify a 231 in the field

Its place in railway operations

A six-axle freight locomotive without train heating is a specialist vehicle with a narrow but important field of use. The high axle count spreads the weight and lowers the axle load, allowing use on lines with a limited permanent way. At the same time, diesel-electric transmission delivers high tractive effort at low speed – exactly what heavy trains need when starting off.

Operationally that meant: block trains, coal and ore traffic, transfers between marshalling yards, plus main-line duties wherever there was no overhead wire. Such workings rarely run to a regular pattern and often occur at off-peak times, which makes them hard to plan for as an observer – a feature that still holds true for heavy diesel traction today. Passenger workings were ruled out because the carriages could not be heated – for the 231 this was a permanent limitation, while the 232 remained flexible.

This specialisation also explains why the class disappeared from the fleet of the Deutsche Bahn AG earlier than its sisters. A locomotive that may only work freight trains is harder to schedule than a general-purpose machine. As soon as freight traffic on non-electrified lines declined and more modern vehicles became available, the decision against the unheated variant followed almost automatically. The same pattern appears at the Bundesbahn: there too, it was the designs without suitable train heating that were withdrawn first.

For observation today: the class has disappeared from active service. Surviving machines are one-off museum examples whose location, owner and condition can change. Always check such information before planning a visit – this applies equally to society premises and to memorial locomotives in public spaces.

Spotting, photography and safety

Looking for a 231 today is a research task rather than a spotting one. Where related six-axle diesels are still in service, the usual rules apply.

• Observation points are platforms, public footpaths, roads and bridges. Track areas, shunting facilities, locomotive depots and stabling sidings are operational or private land and must not be entered.
• Freight traffic needs patience. Block trains and transfers don’t run to a regular pattern; waiting time is part of the deal. How to organise that sensibly is covered in the guide to spotting at a marshalling yard.
• Always photograph the number. With near-identical classes, a close-up of the markings is the only proof. How the twelve-digit vehicle number is structured is explained in the article on the UIC number and its check digit.
• Work systematically. Anyone wanting to tell several classes apart reliably works through features in a fixed order – as described in the guide to identifying locomotive classes.

For memorial and museum locomotives, one more thing applies: the state on display doesn’t necessarily match the last operational condition. Societies often restore a particular era – an earlier livery or an earlier set of markings, for instance. A locomotive can therefore carry markings that only partly match its actual history. Anyone documenting such vehicles is best off noting both: what’s on the vehicle and what’s known about it. Only that way does it stay traceable later what an entry is based on.

Common mix-ups

Conclusion

Today the Class 231 is above all a building block for understanding the German class numbering system: it shows how train heating splits entire classes from one another, how the traction philosophies of the Bundesbahn and Reichsbahn differed, and why so many East German classes have carried a leading 2 since 1992. You won’t meet it in the field any more – but you will meet its sisters, and the same identification rules apply to them.