The European rail network? A real patchwork of technologies…

02/11/2022 – By Frédéric de Kemmeter – Railway signalling and freelance copywriter – Suscribe my blog(Version en français)
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If you think that railways are just about politics and finance, then you’re in for a real treat. Because railway infrastructure is above all national technology, which is an obstacle to standardisation and the European dream of trains without borders. We will explain all this to you very briefly.

Are there so many technical differences between the networks as is often described? Yes and no. Some technical data are common, but others differ. The standardisation of railways will be a very long road, because for decades rolling stock has been built according to the characteristics of the infrastructure.

Since 1922, there has been an international organisation called the International Union of Railways (UIC), whose primary objective is the technical harmonisation of the railway system. The UIC acts as a standardisation organisation and has devised a « UIC Code » consisting of « UIC leaflets », which define common rules for the design, construction, operation and maintenance of the railway system.

International equipment was therefore designed according to the UIC leaflets in order to be able to run from one country to another, at a time when the networks were already designed according to national standards. All the railway vehicles are stamped UIC on their side, with a marking defining the countries in which this railway vehicle can circulate. But what exactly is the situation in terms of infrastructure?

Nobody pays any attention to it. Yet this marking is present on all rail vehicles, both passenger and freight (photo

The track

We have already mentioned this in a previous post. The track gauge is the UIC 1.435mm standard throughout Europe but 7 countries have adopted a different gauge: Finland, the 3 Baltic countries, Ireland, Portugal and Spain. For the last two countries, which export, this is a handicap. For the Baltic countries, it isolates them too much from Europe. For Finland, the country is far from all members of de EU and only has a European border with northern Sweden. As for Ireland, it is an island with no rail connections to the continent.

What about the small narrow-gauge lines? They are local railways serving a local market, and have no need for internationalisation or even national connections over long distances. They live in a closed circuit. These narrow-gauge railways usually arrive at stations shared with the national 1.435mm network, such as Montreux, Chur or St Gervais. In other cases, these local networks have their own station, as in Stockholm for the regional network Roslagsbanan, or the Circumvesuviana, a suburban railway in the Naples area and around Vesuvius.

Loading gauge

It is not to confuse with the track gauge. It’s about the maximum contour (width-height) into which a train must fit, so that it does not touch any trackside, bridge or tunnel elements. This gauge may differ by a few centimetres – or more – from one country to another, as the architecture of platforms and bridges has historically been developed separately in each country. It should be noted that there is also a specific gauge for the pantograph depending on the type of catenary.

Is it a problem? It depends. UIC-stamped cars are said to be able to travel in all European loading gauges without bumping anything. The UIC has codified four gauges in force at international level:

  • the GA gauge, which serves as the basis for the French rail network (in red) ;
  • the GB gauge for certain lines (orange);
  • the GC gauge for the new high-speed lines in Europe (in blue);
  • the GB1 gauge for the transport of large containers (not shown).

These loading gauges all have the same width of 3.29m, and differ only in the high parts, 4.35m for the GA and GB, and 4.70m for the GC. These differences in height explain why, for example, a double-deck car from one country is sometimes not accepted in the neighbouring country.

The different standardised line gauges are now described in the European standard EN 15273, which gives them a legal basis.

The upper part of the gauge, in the shape of a trapezium, is currently causing problems for intermodal transport. Not for sea containers, but for semi-trailers, which have a height of 4m according to European road standards. However, even with the lowest possible wagon chassis, the high corners of these semi-trailers would be likely to exceed the gauge slightly, to « bump into something », hence the non-acceptance of these transports on many lines.

Several networks have adopted a so-called « P400 » gauge on some important lines linking ports to major industrial centres, allowing trains carrying all the semi-trailers in Europe to be accepted.

It should be noted that the very high gauge of certain lines in the USA allows two containers to be stacked on one wagon. This is impossible in Europe…

Traction power

It differs from one network to another because of historical choices linked to the national industry and the technologies at that time. At 1500V DC in the southern half of France or in the Netherlands, 3000V DC in Belgium, Italy, Poland and partially in the Czech Republic, DC was better mastered and formed the basis of electrification in the years 1910-20-30.  

The Germans took another technological turn by adopting alternating current, in 15kV but with a divided frequency. At the end of the 1950s, the French took up the study of alternating current but with a higher voltage, 25kV. In the end, we ended up in the 1960s with four different power supplies in Europe: 1500V, 3kV, 15kV and 25kV. And of course there were a few other exceptions, such as 750V DC in the south-east of England.

The problem? Once you’ve chosen, you build all the rolling stock that goes with it and you can’t go back! So the idea of allowing a locomotive to accept several currents and voltages was considered. This was a great idea, which led in the 1960s to the construction of dual-voltage locomotives, and even three or four-voltage locomotives. The electromechanics of the time showed some limitations, but the technical progress of the 1970s gradually enabled the concept to be mastered and the weight of the traction chains and transformers to be reduced. The Czechs and the French, in particular, used – and still use – dual-voltage/bicurrent locomotives on their respective networks. So did Belgium, the Netherlands, Great Britain, Italy and Spain, with their 25kV high-speed lines.

What’s today? 25kV AC has become the worldwide reference current where relevant. Because with the variety of rolling stock of very different ages within a single country, it is illusory to try to convert an entire network, even in successive phases. The great progress in traction chain and power conversion on board the locomotive remains the answer today at an acceptable price. It is therefore no longer a real problem.


Let’s finish with the biggest piece. Although all networks use red to stop trains and green to say « clear track », over the decades signalling has been enriched by colour palettes specific to each country, producing a variety of interpretations. According to some international drivers (on the Thalys or the Benelux train from Brussels to Amsterdam, for example), learning these interpretations is not yet too difficult. On the other hand, it is the regulations specific to each country that make international driving more cumbersome. As a result, many operators sometimes prefer to change drivers, as in Aachen, Luxembourg, Modane, Brennero or Basel. For the sake of simplicity and avoid costly training.

But signalling is not limited to coloured lights. There is also train detection. This is not done by GPS but by high frequencies sent into the rails. When a train enters a two-kilometre section, the rails are « shunted », causing – to put it simply – an alert signal in the signal cabin saying that this section is occupied. However, certain technical elements of foreign locomotives can sometimes disrupt these frequencies, which is not acceptable in terms of safety.

There is also a repetition in the driver’s cab of the aspect of the signal and the speed control systems. As you may have guessed, all this is done via national technical devices that are all different from one country to another (bottom photo). An international locomotive must therefore be equipped with 2, 3 or even 4 repeater sets if it is to run, for example, like the Thalys, between Paris and Cologne or Amsterdam. This is heavy and expensive. As an example, here is what an international locomotive would have to support as a number of antennas under the chassis to be allowed on foreign networks:

Under a locomotive, a real patchwork…

The adoption of the ETCS (European Train Control System), where there is no longer repetition but orders given directly in the driver’s cab (via a standardised screen), seems to be promising but faces problems of conversion costs on existing lines and rolling stock.


The dream of super railway in Europe should be: GC gauge, 25kV and ETCS. Never mind the speed. But if we can go faster, then let’s do it. Are we going to that?

The theoretical idea is to be able to make a seamless international rail journey. But not everything is international. Many incumbent operators have a national mission, and do not always see the relevance of harmonising everything, especially when international provides a small percentage of overall business.

On the other hand, harmonisation suits the industry’s desire to be able to sell standardised products that allow any entrepreneur to start up or sell a product on a large scale, such as Alstom’s Coradia multiple units or Siemens’ Vectron locomotives. If a sale does not go ahead with one operator, standardised trains can be resold anywhere to other operator, a way of creating a more fluid, seamless second-hand market. A utopia?

For the infrastructure, it was quickly realised that it was illusory to harmonise the entire European network. Europe is therefore trying to harmonise the technique on a series of well-defined corridors by introducing both the GB1 or GC gauge and the ETCS signalling system. Harmonisation of the current is forgotten, as it is no longer a problem as explained above.

But standardisation of existing lines – even limited to corridors – sometimes involves enormous costs, with the addition of major civil engineering work for the gauge, but also because ETCS is used to upgrade a line, for example to increase the radius of curves or to eliminate slow-down zones. In some extreme cases, what lines built 100 or 150 years ago is rebuilt (the commuters network around Brussels in Belgium, for example).

Moreover, the adoption of ETCS means de facto that only rolling stock adapted to this system can run on these lines, which is a handicap because it limits the available equipment. Older « non-ETCS » trains – still numerous in all countries – cannot run on an ETCS-equipped line. As a result, an ETCS train that breaks down cannot be replaced by an older train, for example. The incumbent operators do not like this at all…

The complete standardisation of the railway is therefore still a pious hope and it is rather the technologies that will allow the least expensive possible adaptation from one system of standards to another, particularly when it comes to selling or reselling rolling stock from one country to another.

Yes, with trains, technology will dictate policy. This page has modestly demonstrated this. 🟧

Passage from Belgium to the Netherlands. The track gauge does not change. The loading gauge also not. But everything else changes…

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02/11/2022 – By Frédéric de Kemmeter – Railway signalling
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