Koleje Mazowieckie – KM Sp. z o.o.

Updated: August 2026 – Some trains you can recognise from the silhouette alone, before any marking is even legible. Two rows of windows stacked one above the other, a car body that sags low between the bogies: double-deck vehicles are a defining sight in Polish local rail traffic. Koleje Mazowieckie – KM Sp. z o.o. is the perfect occasion to take a proper look at this body type – and translate the company name along the way.

What is Koleje Mazowieckie – KM Sp. z o.o.?

Koleje Mazowieckie – KM Sp. z o.o. is a Polish local passenger rail company. The name follows a pattern you’ll meet several times in Poland: “Koleje” means railways, the trailing adjective names the voivodeship. “Mazowieckie” stands for Masovia, the region at the centre of the country. The KM carried in the company name itself is the established short form.

Voivodeship railways like this are typically run by the regional self-governments. That places them alongside other local operators that can be found in the same area – such as the city-focused SKM Warszawa or the independent Warszawska Kolej Dojazdowa. Anyone who sees several companies side by side at the same station should therefore never infer the operator from the location, but from the vehicle. Entirely separate from the railway network, meanwhile, is Metro Warszawa, with its own technology and its own fleet.

Why double-deck vehicles define the look of local rail traffic

A train’s capacity hangs on a variable that’s hard to change: platform length. A train mustn’t extend beyond the platform, or boarding and alighting won’t be possible everywhere. Anyone who needs more seats can therefore either run trains more frequently – or build the vehicle taller.

That’s exactly the idea behind the double-deck vehicle: two usable levels stacked within the same structure gauge. The price is stairs inside the vehicle, a more complex build, and longer boarding times, because passenger flows are spread across more space inside the vehicle.

Telling the body types apart

For sightings, it’s not just “double-deck” that matters, but which body type you’re looking at. The distinction is possible from the outside.

Feature	Double-deck coach in push-pull set	Double-deck multiple unit	Single-deck multiple unit
Locomotive at the end of the train	yes	no	no
Driving trailer at the front	often	not applicable	not applicable
Rows of windows	two, stacked	two, stacked	one
Door position	low, between the bogies	low, between the bogies	evenly distributed
Separable in service	coaches can be swapped individually	fixed formation	fixed formation

From vehicle to company

The body type tells you what is running. Who is running it is written on the data panel: country code PL, hyphen, keeper marking, next to the full vehicle number. Liveries are a good first clue, but no proof – they change, and several companies can look similar at the same station. The general approach is described in the guide Who’s actually running it? Identifying railway operators.

Specific vehicles from Polish local rail traffic can be found in the class database – for example the multiple unit 31WE, the locomotive family Newag Griffin, or the classic multiple unit EN71. Many of these vehicles are built by domestic manufacturers such as PESA Bydgoszcz. Which body type runs on which service changes with diagrams and new procurement.

A photographic challenge

Tall car bodies and low-set doors make double-deck vehicles a subject all of their own: up close, the lines tilt sharply; from a distance, the train loses its sense of height. A slightly elevated, publicly accessible vantage point and a slight three-quarter angle almost always help. The basics are covered in the guide How to take good photos of trains. If you also want to understand what the number at the front of the train means, the introduction is in Decoding train numbers.

Structure gauge: why double-deck isn’t possible everywhere

A double-deck vehicle makes full use of the height a line allows – and that’s exactly where the limit lies. Above every track lies an imaginary outline that no vehicle may exceed: the structure gauge. It’s determined by tunnels, bridges, platform canopies, signal gantries and the height of the overhead line. Where this outline is tight, a second level simply can’t be fitted in. It is set and maintained by the infrastructure manager, in Poland by PKP Polskie Linie Kolejowe.

That explains why double-deck vehicles aren’t equally common everywhere in Europe, and why a vehicle that runs without issue on one network can’t be used on another. The body type is therefore not just a question of demand, but first and foremost a question of infrastructure.

Limiting factor	Effect on the body type
Tunnel cross-section	limits the overall height of the car body
Height of the overhead line	determines how much space stays free above the roof
Platform edge and height	affects the position of the doors and the lower deck
Bridges and overpasses	individual pinch points can close an entire line
Curve swing on bends	wide, tall bodies need more lateral clearance

For observation, this is a useful connection: if you only ever see single-deck vehicles on a line, that doesn’t necessarily come down to the operator. Equally, you can’t infer a particular company from the use of double-deck vehicles – in Polish local rail traffic several companies operate alongside each other, including, nationwide, Polregio. The body type describes the line and the demand, not the company.

Common mix-ups

• Driving trailer and multiple unit. Both have a smooth front end. The locomotive at the other end of the train settles it.
• A tall car body doesn’t mean double-deck. Some single-deck vehicles just look tall. Count the rows of windows.
• KM and other companies at the same station. The location says nothing about the company.
• Sp. z o.o. and S.A. – both Polish legal forms, but not the same. The suffix is part of the company name.
• Regional and long-distance services. Both use the same lines; the service category shown at the front of the train and the vehicle’s body type separate them.

Verdict

Koleje Mazowieckie stands for two things you can learn in an afternoon: how a Polish voivodeship name is put together – and how to reliably tell double-deck vehicles from single-deck ones, and locomotive-hauled trains from multiple units.