Interoperability means that a train could run freely and in perfect safety on any line in the European Union. The aim is seamless operation for rolling stock and for infrastructures, which should be fully compatible with and accessible to any train. This cooperative mindset is moving European regulations gradually towards harmonization.

In the beginning, each country built its own railway. To this day, the gauge for some lines in Spain is different from the gauge in France, and there are different signalling systems, safety systems and more. For example, to run a train in every part of Europe, you’d need 6 or 7 onboard safety systems. It’s unmanageable, both economically and technically.

It started with political will and legislation. For example, Directive 91/440¹ of 1991 separated managing rail infrastructure from managing transport service operations, opening the door to market liberalization. The aim was to simplify customer access to trains and streamline freight rail traffic throughout Europe. From the start, the European Union has understood the economic advantage of a continent-wide network.

Under the European Green Deal, which targets carbon neutrality by 2050, the European Union has identified trains as a solution in the fight against climate change. That makes interoperability even more valuable, since it will boost rail performance and efficiency.

It takes the form of ‘railway packages’, which modify European regulations. The First Railway Package² was passed 10 years after Directive 91/440¹—the time it took for the European Commission to move from political will to taking action and addressing technical issues. In 2001, the first package liberalized international freight transport, opening the market to competition. In 2004, national freight markets were completely liberalized.

True, but the European Commission wanted to do the same for passenger rail. That led to the Third Railway Package in 2007, which liberalized the international passenger market. The fourth package, adopted in 2013, opened up the passenger market completely, without regard for borders.

Any company that wants a market position—and that includes SNCF and all the other French and foreign operators—has a responsibility to promote the transition to a single European railway area. Which is why Europe-wide technical regulations are so important.

The aim of the technical specifications for interoperability, or TSIs, is to create a single set of rules for all member countries. For example, companies could operate the same trains anywhere in Europe, without spending money to convert them. There’s also the question of performance—of serving customers well. That’s important for everyone in rail. Having a single set of regulations would help companies improve their intrinsic performance, because regulations would no longer be a differentiator.

Today, we have 11 TSIs, set by the EU and grouped by topic. One covers rolling stock, another describes the technical characteristics of wagons, and third focuses on infrastructure. Other TSIs concentrate on service, safety, day-to-day operations, etc. The interoperability directive, updated in the Fourth Railway Package, opened the door to working on the technical side.

Take innovative rolling stock projects like TELLi, DRAISY and FLEXY—all designed to serve rural communities. Here, we have to consider European regulations. Do we need to create a new regulation, or add new specifics to an existing one? You have to choose—or you can leave the regulations alone. Sometimes the EU decides not to impose a technical regulation on operators.

Operators can agree to work on a standard together and then require compliance in their contracts with rolling stock and track manufacturers. Also, thanks to the International Union of Railways (UIC)³, a lot of standardization work has been done without benefit of European regulations. Rail operators haven’t waited for the EU to start building a European rail area. But regulations make compliance mandatory.

The first question is ‘Do we need to create a standard?’ Let’s go back to DRAISY as an example. Eventually we’ll export it, so we need to draft standards for its battery power system, charging sockets, gears, onboard signalling systems and so on. Then we ask, ‘Do these standards need to be incorporated into EU regulations?’ All of us work together, focusing on European innovations, international standards, and EU regulations.

Yes. They think about how an innovation will affect the regulations, and later they defend SNCF’s interests. We tap into the full range of expertise within SNCF Group. We have employees who are free to imagine the new systems of the future, and then our technical experts and draughtspeople convert their ideas into an industrial reality. Take TELLi: maybe one day we’ll need to modify the TSIs to scale it up for mass production in a factory.

Everything goes through the European Union Agency for Railways (ERA)⁴, the entity that prepares the TSIs. We work with them through some 15 associations that represent the rail sector and can negotiate the content of the regulations with ERA. We also work with ERA through national safety authorities, because the agency handles safety as well as interoperability.

We’ve been in talks with ERA about the content of all 11 TSIs since 2019, and the agency is preparing its draft versions. These will be submitted to the European Commission for discussion with the member states—including France, of course.

The technical experts have done their work, and the ball is now in the decision makers’ court. Our role is to support the French State step by step, by providing a full technical analysis of all the drafts produced by the European Commission. We want the State to be aware of the long-term consequences of each TSI’s components before it makes any decisions.

In 2012, the EU opted to replace the tail lamps⁵ of freight trains with painted plates. Because the plates have no batteries or lamps, they’re harder to see, so the lamps at the front were required to generate more light. This change would have been mandatory as of 1 January 2026, and it would have been costly. We inserted a request that the lamp upgrade be as inexpensive as possible, and ERA accepted it. This will save SNCF €40 million, and it will also benefit RATP and other transport authorities⁶.

There’s a lot of work on digital automatic coupling (DAC). We’ll be able to use it anywhere in Europe to couple and decouple wagons, leave them in a yard, send them off with the rest of a train, and more. It’s a critical link in the chain. If we want to run more trains on the European network, we have 2 options: build new track, or use the track we have more efficiently.

Yes. If we can use the existing track more efficiently, so much the better. To increase the number of trains, we need to reduce the headway between them, and that means we need data on train integrity. DAC will relay this critical information. Passengers will also benefit from having more trains on the same network. These innovative ‘technology bricks’ meet a specific need, and they’ll be useful for other sectors of the rail system too.

Yes. Train integrity data will support operation of Level 3 ERTMS. Today’s network is divided into fixed segments, each a few km long. When one train is in a given block, no other train can enter it, so a 50-m train can occupy an entire 5-km segment. Level 3 ERTMS will change that.

With Level 3 ERTMS, we can have moving blocks—essentially safety bubbles around each train. This part of the technology isn’t quite finished, but the specification work is making good progress. For the train to run safely inside its bubble, all we need to know is its length and location, and we can use innovative technologies to pinpoint the exact position of each train.

Deploying ERTMS throughout Europe means that we’ll have a single safety system instead of 6 or 7 different ones. For the European Commission, the priority is to roll out ERTMS on heavily used networks, freight corridors and high-speed lines. In France, we aim to deploy it on 17,000 km of line. Meanwhile, we’re gradually upgrading trains thanks to funding in the ERTMS deployment plan. Each member state is responsible for that.

Each member state will be required to publish a national plan to deploy ERTMS. This will explain how they’ll roll it out, on which lines, how they’ll pay for it, and so on. In France, the State will bear full responsibility, for deployment, and it will be expensive.

Yes, because it will simplify our systems. But it will take huge upfront investments. To adopt ERTMS, we need to upgrade both trackside equipment and rolling stock. ERTMS-enabled trains can’t run until we install the system in the track too. Until we’ve done that, trains will need to have both the legacy system and new one to stay in operation.

Right. You make the investment upfront, knowing that it won’t pay off until later. Take the Marseille-Ventimiglia line: SNCF Réseau has opted to install ERTMS and retire the old signalling, so only ERTMS-capable vehicles will be able to run on that part of the network. But to serve other parts of the network, operators will need to have both ERTMS and the legacy systems. In the beginning, all we’ll see are the costs. But one fine day, the whole network will have ERTMS, and the old national safety systems will have disappeared. It’ll take a lot of work and cooperation to get there.