SZ 610 (Stadler FLIRT DMU)

Updated: August 2026 – A local-service train with a modern design and low entrances, but no pantograph on the roof: that’s Class 610, Slovenia’s diesel multiple unit based on the FLIRT platform. It serves the lines where no overhead wire hangs, and it’s a good example of why, when identifying a vehicle, you should look at the roof first and not at the design.

What is Class 610?

SŽ Class 610 is a diesel multiple unit for regional and local services, built on the FLIRT platform from Stadler Rail in its diesel-powered version. It belongs to the newer vehicle generation of Slovenske železnice and takes on duties on lines that have no overhead line.

The traction equipment is on board the vehicle itself, so the train is independent of the electrified network. Unlike electric multiple units, Slovenia’s 3 kV DC electrification system plays no role for Class 610 – in principle it can run on any line it is approved for, with or without overhead wires.

Diesel or electric? The first glance goes to the roof

With modern local-service vehicles, diesel and electric variants of the same platform are hard to tell apart from the outside. The same front end, the same window layout, the same interior concept – the difference lies in the traction equipment.

Feature	Electric multiple unit	Diesel multiple unit
Roof	Pantograph fitted	No pantograph, exhaust and radiator openings instead
Traction equipment	Under the floor and on the roof	On the FLIRT design, in its own short module within the train formation
Area of operation	Only under the wires	Independent of electrification
SŽ class number	Starts with 3	Starts with 6 or 7
Sound	Quiet pull-away, mostly rolling noise	Clearly audible combustion engine

The short power module is the most eye-catching visual feature of the diesel variant: between the longer vehicle segments sits a visibly shorter section that houses the equipment. Once you’ve noticed it, you’ll recognise the design reliably from then on.

If you want to apply this approach to other countries and vehicles, the guide to identifying rolling-stock classes sets out the general method – it works regardless of each country’s numbering scheme.

Where diesel multiple units work in the Slovenian network

Slovenia has electrified its main routes, but not every line. That’s exactly where Class 610 comes in. On these lines it replaces older vehicle generations and brings a standard of comfort that was previously reserved for electric vehicles.

This results in a clear division of labour within the fleet: electric multiple units such as Class 312 serve the electrified regional lines, older diesel railcars such as Class 711 represent the previous generation on the same branch lines, and heavy diesel locomotives such as Class 664 handle freight and engineering trains without overhead wires.

Why diesel multiple units are built despite electrification

At first glance it seems contradictory to procure new diesel vehicles in the middle of the electrification debate. Operationally, it isn’t. Electrification only pays off above a certain traffic density: overhead line, substations and maintenance cost the same whether twelve or a hundred trains run a day. On lightly used lines, a vehicle that is independent of the electrified network is therefore the more economical solution.

There’s also a practical advantage: diesel vehicles can be used flexibly. They can run under a switched-off overhead line during engineering works, divert onto alternative routes and serve routes that are partly electrified and partly not. An electric multiple unit doesn’t have this option – for it, every line ends where the overhead wire ends.

For observers, that’s exactly what makes it interesting. A modern diesel multiple unit isn’t a step backwards, but a deliberate choice for a specific transport task. And because both variants of the same vehicle family look very alike from the outside, a station where both call gives you a direct comparison: the same shape, different technology. If you photograph both vehicles side by side, you’ve documented the difference between network-dependent and self-powered traction in a single picture.

Spotting, photography and documentation

Branch lines are rewarding for photographers: little overhead equipment in the frame, often beautiful scenery, manageable traffic. The price is a sparse timetable – if you turn up unprepared, you’ll wait a long time.

• Check the timetable for the location. On branch lines, the timetable decides your day. One or two trains an hour are more the exception than the rule here.
• Compose without overhead wires. Non-electrified lines allow compositions that don’t work under catenary – use that for clean silhouettes.
• Show the power module. If you want to document the design, choose a crop in which the short module within the train formation stays visible.
• Use your image data. Capture time and camera data are stored in every file. How to use them for matching sightings is explained in the article on EXIF data for spotting.

For unambiguous identification, the vehicle number remains decisive. The guide to the UIC number and its check digit shows how the twelve-digit number is structured and where the country code appears – for Slovenian vehicles, 79.

Common mix-ups

Conclusion

Class 610 shows what modern local services look like on non-electrified lines: the same vehicle platform, the same comfort, just with its own traction on board. For identification, that means design and interior tell you nothing about the type of traction – the look at the roof decides, the class number confirms. And because the class belongs to a recent procurement, its area of operation keeps shifting; current information matters more here than any list.