Key takeaways
- RET stands for Rotterdamse Elektrische Tram – the operator of Rotterdam's public transport.
- Citadis is an Alstom platform that runs in many European cities, each in an adapted version.
- Tram, not railway: different regulations, different numbering systems, different electrification system.
- Don't confuse it with the metro: RET operates both, but the vehicles are fundamentally different.
- The fleet and route allocations change – check the current situation before a targeted trip.
Contents
Fact file
| Vehicle type | Low-floor tram (articulated railcar) |
|---|---|
| Operator | RET – Rotterdamse Elektrische Tram |
| Vehicle platform | Citadis by Alstom |
| Area of operation | Rotterdam tram network |
| Electrification system | DC supply of the urban tram network, considerably lower than on the railway |
| Design principle | multi-section articulated vehicle with a continuous low floor |
Identifying features
Is this really the class in front of you?
- Multi-section articulated vehicle with short sections and bellows between them
- Continuous low floor and doors directly at street level
- Runs in the street, at stops without a platform edge in the railway sense
- RET running number instead of a UIC vehicle number
- Pantograph for the low DC voltage of the urban network
- Styling suited to city traffic, with large windows and all-over advertising as standard
Updated: August 2026 – A low-floor articulated tram easing its way through Rotterdam’s streets: that’s the RET Alstom Citadis. For spotters from the railway world it’s an instructive case, because almost everything works differently here – numbering system, power supply, regulations and photography. This page places the vehicle in context and shows what you need to look out for.
Spotted a tram? Note the car number.
With trams, what counts is the running number – and the changing wrap. Traintrack records both together.
What is the RET Alstom Citadis in Rotterdam?
The Citadis is a low-floor tram that runs in Rotterdam for RET. The abbreviation stands for Rotterdamse Elektrische Tram, the city’s transport operator. Citadis, in turn, isn’t a type designation in the strict sense but the name of a vehicle platform from Alstom, from which trams for many European cities have been derived.
That gives you the most important distinction straight away: RET is the operator, Citadis the platform. Together they describe the vehicle – just as railway company and class belong together for railway vehicles.
A tram is not a railway vehicle
If you come from the railway world, it’s easy to underestimate how fundamentally the two systems differ. Three points are decisive for identification.
First, the numbering system. Railway vehicles carry a twelve-digit UIC number with a country code – in the Netherlands that’s 84. Trams have a running number from the transport operator instead. If you’re used to relying on the UIC number for confirmation, you’re missing that tool here. How the UIC system works in the railway sector is explained in the article on the UIC number and its check digit.
Second, the power supply. The Dutch railway network uses 1.5 kV DC. Urban tram networks use a considerably lower DC voltage. A vehicle therefore can’t simply switch from one system to the other, even if the track gauge were the same.
Third, the operating environment. Trams partly run on line of sight in the street. That shapes vehicle width, braking behaviour, door arrangement and – very practically for you – the question of where you can take photos at all. While the railway spotter looks for a fixed viewpoint on the platform, in the city you work more flexibly: the tram comes to you, but the background changes with every street corner.
In practice this means: don’t simply carry over your habits from the railway world. Counting axles hardly gets you anywhere with articulated vehicles; the number of sections and the bogie arrangement are much more telling. And instead of a class list, you need the fleet overview of the respective transport operator.
Count the sections
How many sections does the vehicle have, and how many bellows are there between them? For trams, that's the equivalent of counting axles on locomotives.
Check the floor height
A continuous low floor with doors at street level marks modern low-floor vehicles. High-floor designs look noticeably bulkier.
Look for the running number
It's usually on the front and the side wall. Without it, a sighting in a fleet with changing all-over advertising is hard to assign later.
Context: where and how to watch Rotterdam’s trams
Tram spotting works differently from railway spotting. The vehicles are frequent, but viewpoints are scarce: the urban setting rarely offers clear lines of sight.
| Observation situation | Chance of a sighting | What matters |
|---|---|---|
| Central stops where several routes converge | high | Many vehicles in a short time, but a busy background |
| Segregated track outside the centre | high | Clearer lines of sight, calmer background |
| Narrow streets | medium | Subject often only partly visible |
| Depots and stabling sidings | – | Private land, no access; can only be viewed from outside |
| Railway stations | low | Different system, different vehicles |
Fleet and route allocations change
Which vehicle types run on which routes changes with procurements, refurbishments and operating conditions. Check the current situation instead of relying on older lists.
The neighbouring Dutch cities run their own vehicle families: Amsterdam has the GVB CAF Urbos, The Hague the HTM Avenio from Siemens. If you want to jump back to the railway, the NS SLT is the matching counterexample – a vehicle with a UIC number, platform operation and 1.5 kV DC.
Collect tram sightings in a structured way
Car number, route, wrap and date in one place – that keeps even a large city fleet manageable.
Photography in the city
The hardest part of tram photography has nothing to do with the vehicle, but with everything around it.
Choose the background first
Find a spot with a calm backdrop and wait there for the vehicle – not the other way round. The background makes the picture.
Watch out for overhead lines and poles
In the city, overhead wires and poles cut across the subject. A slightly shifted viewpoint often solves this better than any post-processing.
Don't step onto the track area
Even street-running track is operational railway land. Photograph from the pavement or from permitted areas and keep an eye on moving traffic.
Document the wrap
All-over advertising changes frequently. A picture of the entire side wall makes the sighting considerably more valuable later.
Specific shooting techniques for trams are covered in the guide to good photos of trams. How to record sightings in urban public transport systematically is shown in the article on the app for tram spotters. For the methodical groundwork, the guide to identifying classes is also worthwhile – the approach can be transferred to trams.
Understanding platforms: why trams across Europe look related
Citadis isn’t a single vehicle type but a modular kit. This principle shapes the European tram market so strongly that it’s worth taking it apart once.
What’s standardised. Bogies, traction equipment, control systems and the basic body structure come from a shared kit. That lowers development costs and makes spare parts available across city boundaries.
What’s individual. Length, width, number of sections, door arrangement, interior and above all the front-end design are adapted for each customer. Many cities attach great importance to a distinctive look, because the tram is part of the city’s identity.
What that means for you. Two Citadis vehicles from different cities may hardly look related at first glance – and yet technically they are. Conversely, you can’t conclude from a similar front end that it’s the same platform. Identification only becomes reliable through the number of sections, bogie arrangement and proportions, supplemented by the running number.
You’ll find the same pattern with other manufacturers: the GVB CAF Urbos in Amsterdam and the HTM Avenio in The Hague represent two more major European tram kits. Once you’ve looked at all three side by side, you’ll recognise the typical platform features much faster afterwards.
Common mix-ups
It points to a Citadis tram if …
- it's a multi-section low-floor articulated vehicle
- the vehicle is running in Rotterdam's streets
- an RET running number is marked instead of a UIC number
- the doors are at street level
Look more closely if …
- all-over advertising obscures the styling
- you see several generations of trams on the same network
- the vehicle runs on segregated track and therefore looks more like a railway vehicle
It's not a tram if …
- the vehicle stops at high platforms on the metro network
- a twelve-digit UIC number is marked
- the train runs on the railway network under 1.5 kV DC
Conclusion
The Rotterdam Citadis is a good training subject for anyone who wants to extend their spotting beyond the railway. Operator and platform instead of class, running number instead of UIC number, city streets instead of platform: once you’ve thought these shifts through, you’ll find any European tram network easier.
In short
Multi-section low-floor vehicle, RET running number, urban DC network: that's the Rotterdam Citadis. Note the car number, route and wrap – the latter in particular changes faster than you'd think.
From the platform to city transport
Trains, trams and buses in one log – so your sightings aren't spread across several systems.
Summary
- The Citadis in Rotterdam represents a tram platform found all over Europe, in a version specific to the country.
- If you want to identify trams, you work with different features than for railway vehicles: number of sections, floor height, running number.
- In the city, the viewpoint makes the picture – not the focal length.
- Sightings should include the running number and date, because advertising wraps change frequently.
Frequently asked questions
What does RET stand for?
RET stands for Rotterdamse Elektrische Tram. The company runs urban public transport in Rotterdam. Despite the historic name, its operations now cover several modes, including tram and metro. For identifying vehicles, the key point is: RET is the operator, not the vehicle type.
What is the Alstom Citadis?
Citadis is a tram platform by Alstom. Platforms are modular kits: the basic structure, bogies and traction equipment are standardised, while length, width, interior and design are adapted for each city. That's why Citadis vehicles from different cities look related but not identical.
Is the Citadis a tram or a metro?
A tram. RET does also operate a metro network, but other vehicles are used there. Trams run in or alongside the street, stop at stops without a platform edge in the railway sense and follow different regulations from railway vehicles.
Why does a tram not have a UIC number?
Because the UIC numbering system is intended for railway vehicles. Instead, trams carry running numbers from their respective transport operator. For your records, that means you note the car number, not a twelve-digit vehicle number. The country code 84 for the Netherlands plays no part here.
Does the Citadis run on the same power supply as the railway?
No. The Dutch railway network uses 1.5 kV DC, urban tram networks a considerably lower DC voltage. That's one of the reasons why trams and railway vehicles aren't technically interchangeable, even where the track gauge matches.
Can I see the Rotterdam Citadis in Germany?
The Rotterdam vehicles stay on their own network. Citadis trams as a platform, however, run in numerous European cities, each in its own version – you recognise the family resemblance by the proportions and the arrangement of sections, not by an identical appearance.
What makes tram photography special?
The urban setting. Unlike on a platform, you rarely have a clear view: poles, cars, pedestrians and billboards compete with the subject. Good tram pictures therefore usually come from the viewpoint rather than the equipment – choose the background first, then the vehicle.
Why is it worth documenting advertising wraps?
Because they're short-lived. All-over advertising is the norm in urban public transport and often changes after a few months. A sighting with car number, date and wrap therefore records a state that won't be repeated – and for archives, that's exactly the valuable information.
Log your sighting of the RET Alstom Citadis (Rotterdam)
Date, location and vehicle number logged in seconds – and visible to the community.
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