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Lyon-Turin: What will the world's longest rail tunnel be used for?

Written by Sophie Renassia

Published today

A project launched 35 years ago, a budget that keeps climbing, regular protests on both sides of the Alps, and an XXL ambition: digging the longest railway tunnel in the world. No, it's not some billionaire's wacky scheme: it's the Lyon-Turin, probably Europe's most controversial railway project.

On paper, though, it has everything we love about HOURRAIL!: a train linking Paris to Milan in four hours and trucks loading onto freight cars. So why does this project divide people so much? Lisa dug into the subject with Thierry from the YouTube channel Aiguillages. Here's the breakdown

The Lyon-Turin, what exactly is it?

A 270 km line and a record tunnel under Mont-Cenis

The Lyon-Turin is a new railway line of about 270 km between Lyon and Turin, for both passengers and freight. It's broken into three pieces: the French section between Lyon and Saint-Jean-de-Maurienne (about 160 km, entrusted to SNCF Réseau), the Italian section up to Turin (about 50 km, entrusted to RFI) and, between the two, the 65 km cross-border section, run by TELT.

It's the one drawing all the attention: a 57.5 km base tunnel under the Mont-Cenis massif, between Saint-Jean-de-Maurienne in Savoie and Susa in Piedmont. It stretches 45 km through France and 12.5 km through Italy. Once completed, it will dethrone the Gotthard Base Tunnel (57.1 km) as the longest railway tunnel in the world.

That title, however, comes down to a matter of a few kilometers. The Brenner Base Tunnel, between Austria and Italy, also expected in 2032, measures only 55 km between its portals. But its promoter claims 64 km of continuous underground link when counting the Innsbruck railway bypass, opened in 1994. So it all depends on what you measure: in the strict sense of a base tunnel, Mont-Cenis will remain the longest.

Two tubes and 164 km of galleries

Initially, a single tunnel was envisioned. But European safety rules changed, notably after the Mont Blanc Tunnel disaster in 1999. The result: we're digging two side-by-side tubes, one for each direction of travel, connected by safety cross-passages. In the event of an accident, passengers can be evacuated to the other tube, and an incident no longer blocks the entire structure.

That's reassuring, but it completely changes the scale of the project: with the access shafts and service galleries, we now have to dig 164 km of galleries. And the reference cost of the tunnel, certified in 2015, climbs to €8.6 billion.

TELT, the French-Italian project owner

The construction site is led by TELT (Tunnel Euralpin Lyon Turin), a company equally owned by the French state and the Ferrovie dello Stato Italiane, Italy's equivalent of our SNCF. Planned by the 2012 Franco-Italian Rome agreement, it was created in 2015, the year the two countries signed the definitive commitment to the works.

Before it, Lyon-Turin Ferroviaire (LTF) managed the project. But LTF had been designed for studies and geological surveying, not for building a construction site of this scale. A structure capable of taking action was needed.

35 years of history: a project that changed face along the way

From the Viterbo summit to the Mont Blanc disaster

It all begins in October 1991, at the Franco-Italian summit in Viterbo: France and Italy launch a feasibility study for a rail link under the Alps. In 1994, at the Essen European summit, the Lyon-Turin line enters the list of 14 priority projects of the brand-new Trans-European Transport Network (TEN-T). It is no longer just French-Italian: it becomes a European project. But despite this label and the first studies, it stalls for years.

Until March 24, 1999. That morning, a heavy goods vehicle catches fire in the Mont Blanc road tunnel. The fire lasts 53 hours and kills 39 people. The tunnel stays closed until March 2002, and about 90% of the trucks that used it shift to the Fréjus road tunnel, in the Maurienne valley. It is this road chaos that truly revives the rail tunnel project.

From passengers to freight, then to climate: a narrative that shifts

At first, the idea was simple: bring Lyon closer to Turin, Paris closer to Milan, and better connect the two sides of the Alps for passengers. Today, official press releases mostly talk about freight, a great European corridor between Lisbonne and Budapest, and the climate emergency.

This shift is no small matter. When passenger traffic forecasts were revised downward, the freight argument became central. When the economic case was challenged, the climate argument took up more and more space. That doesn't mean these arguments are false: freight and climate are real issues. But one can legitimately wonder whether the project met a clear need from the start, or whether the narrative adapted over time to defend a construction site already underway.

2015, 2030, 2033… and maybe later

In 2001, at the Franco-Italian summit in Turin, the tunnel's opening was set for 2015. During the European Court of Auditors' audit in 2020, the deadline was pushed back to 2030. It is now set at 2033. Compared to the initial promise, that's 18 years of delay. TELT, for its part, reasons from the more recent contractual schedules, and therefore acknowledges only a limited delay.

And even the 2033 horizon looks fragile. In May 2026, the Conseil d'orientation des infrastructures (COI) judged the delivery schedule unrealistic. In July, Le Monde revealed that the tunnel boring machine Viviana had completed only 3% of the planned excavation in nine months, pointing to at least two more years of delay. According to TELT, the tunnel boring machine finally crossed this fault zone in October 2026 and resumed its excavation pace.

Above all, a tunnel is useless without the tracks leading to it. On the Italian side, the roughly 50 km section must follow the tunnel's schedule. On the French side, the some 160 km of new line between Lyon and Saint-Jean-de-Maurienne still have no schedule, and the scenario adopted by the COI in 2023 pushed their delivery back to 2045. Their public utility declaration expires in 2028, and the extension file has been under review at the Conseil d'État since the summer of 2026. In the meantime, trains will use the historic line, which SNCF Réseau is already connecting to the future tunnel at Saint-Jean-de-Maurienne.

How much does the Lyon-Turin cost, and who pays?

€11.1 billion for the tunnel, around €30 billion for the whole project

The budget for the base tunnel has risen from €8.6 billion in 2015 to €11.1 billion in 2024, according to the update published by TELT. And that's just the tunnel. The Italian access sections are estimated at around €2 billion, and the French access sections at €7.2 billion, according to figures presented in September 2026 at the general assembly of La Transalpine, the association bringing together the project's supporters.

Back in 2012, the Court of Audit already estimated the overall cost of the link at €26 billion. No official overall estimate has been made public since, but in public debate, €30 billion is often mentioned, factoring in inflation and rising material costs.

European, Italian and French funding

The European Union is the lead funder: since a Commission decision in July 2025, it can cover up to 55% of the cost of the base tunnel and 50% of that of the access sections. The rest is shared between Italy and France, with Italy bearing the largest share. The Commission also presents it as a flagship project of the trans-European transport network, at the heart of the Mediterranean corridor. Since 2014, the EU has committed more than €1.5 billion to it, including €700 million allocated in 2024: the third-largest envelope among the 134 projects selected that year.

18% or 30%: how far along is the construction?

It all depends on what you measure. If you look at the two tubes of the base tunnel, about 22 km have been dug out of 115, which is just under 20%. If you count all the galleries (access shafts, exploration galleries, safety adits), TELT reports more than 50 km out of 164 as of mid-October 2026, which is around 30%. Opponents highlight the first figure, promoters the second, and both are true.

A project presented as irreversible

Despite everything, the construction is expected to run its course. In July 2025, the European Commission adopted an implementing decision that sets, together with France and Italy, the list of works, their schedule and their governance. The two countries must report annually on their progress and justify any delays.

For its supporters, the Lyon-Turin is therefore irreversible. For its opponents, it is precisely this lock that is the problem: a project launched 30 years ago keeps moving forward even though its very rationale is disputed. This decision is also due to be re-examined at the end of 2026, to take into account the actual state of the studies and works.

What will the Lyon-Turin tunnel actually be used for?

For travelers: Paris-Milan in four hours

This is the most consensual argument: according to the Ministry for the Ecological Transition, Lyon-Turin would drop from more than 4 hours to just under 2. Paris-Milan, which today takes about 7 hours by TGV INOUI or Frecciarossa, would fall to just over 4 hours, city center to city center. Some opponents, however, dispute these estimates and believe the actual gain is far more modest.

And this time saving is no small thing. With 2.4 million passengers a year, Paris-Milan is the third most-traveled air route from France to Europe (Eurostat data cited by Réseau Action Climat in 2025). Yet when you factor in the trip to the airport, check-in, security checks, and the shuttle into central Milan, the advertised hour and a half of flight time stretches considerably. The Eurostar precedent showed it: when the train becomes competitive on a route, a large share of travelers switch.

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The Fréjus tunnel already exists, but it has its limits

If the project is divisive, it's notably because a Franco-Italian rail corridor already exists: the Fréjus tunnel, 13.7 km long, between Modane and Bardonecchia. Opened in 1871, it has since been electrified (between 1912 and 1920) and then widened in 2010 to accommodate the rail motorway. It still carries passenger trains, freight, and even the Alpine rail motorway, which loads trucks onto wagons.

Its limits are nevertheless very real: a mountain line with steep gradients, a winding route, and freight trains shorter than the European standard of 750 meters. And above all, rail freight there has dropped sharply: more than 9 million tons in 1998 via Modane, compared to 3 to 4 million per year between 2011 and 2021 across all Franco-Italian rail crossings (Transalpine Observatory, Savoie Department).

Hence the opponents' question: why build a new tunnel costing several billion when the old one isn't even at capacity and could be modernized? That was in fact the approach the COI favored as early as 2018 for access routes, with the modernization of the existing Dijon-Modane line. For the project's defenders, the issue isn't available capacity but performance: you can't run long, heavy, competitive freight trains on a mountain line this steep.

Freight: Enormous Potential, and a Paradox

In 2021, around 3 million heavy goods vehicles crossed the Franco-Italian border (Transalpine Observatory, Savoie Department). The project's promoters aim to shift one million trucks a year onto rail; the Ministry of Ecological Transition, more cautious, projects 700,000 by 2035. But if the potential is so great, why is rail already losing so much ground on this route?

This is the real heart of the matter: the Lyon-Turin is not just a debate about a tunnel, it's a debate about our ability to organize a modal shift. A tunnel, even a high-performance one, isn't enough to get goods onto trains. You also need competitive prices, operators ready to use it, available track slots, logistics platforms, taxes that weigh more heavily on road transport, and a strategy that holds up over time.

Switzerland: Same Mountains, Different Policy

The comparison with Switzerland is telling. There, across the Alps, rail carries 68% of goods (first half of 2026, according to the Federal Office of Transport). The country opened three major Alpine rail tunnels between 2007 and 2020 (Lötschberg, Gotthard, Ceneri), but above all, it pursued a very assertive policy to discourage road transit, including a heavy goods vehicle charge.

Same mountains, same geographic constraints, opposite result. Even there, mind you, nothing is guaranteed: rail's share slipped slightly in 2026. Further proof that infrastructure alone isn't everything.

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Why Is the Lyon-Turin So Hotly Contested?

The Ecological Paradox of Rail

The Lyon-Turin is presented as an ecological promise: fewer trucks, more trains, less CO2. And yet, it has been contested for decades by a segment of the environmental movements. The reason is simple: before you can run trains, you have to dig through the mountain, move millions of tons of material, pave over natural land, expropriate residents, and cut through fragile natural habitats.

That's the whole paradox of rail: trains are far less carbon-intensive in use, but building them involves massive construction projects. So the real question becomes: after how long is the impact of the construction site offset by the avoided emissions? To answer that, we need solid, transparent, up-to-date studies that cross-reference costs, actual expected traffic, avoided emissions, and damage to local areas. Let's be clear: at HOURRAIL!, we champion trains, and that's exactly why we refuse to consider a rail construction project low-carbon by default. It only is if its benefits truly end up outweighing its impacts, and on the Lyon-Turin, that demonstration remains to be made.

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A carbon debt of 15, 25, or 50 years

Building the link and its access routes would generate approximately 10 million tonnes of CO2. According to the European Court of Auditors (2020 special report), these emissions would only be offset 25 years after the line opens, and even 50 years if traffic reaches only half of forecasts—forecasts it already considered optimistic. TELT, for its part, puts the figure at 15 years. With the line opening in 2033, followed by French access routes much later, the net climate benefit would therefore not arrive before mid-century. And the most pessimistic scenario is far from theoretical: the European Court of Auditors noted that the target of 24 million tonnes of freight by 2035 represented eight times the traffic at the time. Yet Franco-Italian rail freight plateaued at between 3 and 4 million tonnes per year between 2011 and 2021.

Water, the other hot-button issue

Boring 57.5 km under an Alpine massif inevitably means crossing groundwater tables. In 2003, in Villarodin-Bourget, in the Maurienne valley, a village spring suddenly dried up during the digging of an exploratory tunnel. Lyon-Turin Ferroviaire, then the project owner, must build a new drinking water supply for the village of Bourget. Since then, according to opponents, dozens of springs have dried up or lost flow in the valley. In 2022, TELT even planned emergency measures, up to and including water tankers if necessary, to secure drinking water in the Maurienne. When the project owner itself has to consider water tankers for an Alpine valley, the impact on water is no longer hypothetical.

Opponents also cite the figure of 1,500 hectares of farmland and natural land sealed across the entire project. For reference, the 2012 public inquiry estimated the agricultural footprint at 680 hectares for the French section alone, between Grenay and Saint-Jean-de-Maurienne. On top of that are millions of tonnes of spoil to manage in valleys already saturated. TELT, for its part, says it reuses more than half of the excavated material in building the structure, claims that protecting natural resources is a priority, and highlights its 130 water monitoring points.

No TAV: the Susa Valley on the front line

It's on the Italian side that the fight is fiercest, in the Susa Valley, an Alpine valley between the border and Turin. That's where the No TAV movement was born (short for No al Treno ad Alta Velocità, "no to high-speed rail"). For many residents, the project came from above, with no real consultation, into a valley already crossed by a motorway, a national road, and a railway line.

The opposition there is also about identity: many residents refuse to let their valley be reduced to a mere thoroughfare. For the promoters, the valley is a strategic link in a European corridor; for some of its residents, it is first and foremost a place to live. The mobilization remains strong: on July 25, 2026, a violent protest caused around €1 million in damage at the Chiomonte construction site, acts condemned by the project's stakeholders.

In France, activists and local officials step up

On the French side, the protest came later, carried by collectives such as No TAV Savoie or Vivre et Agir en Maurienne, and by movements such as the Soulèvements de la Terre, Extinction Rebellion, Friends of the Earth or the Confédération paysanne.

On June 17 and 18, 2023, an international mobilization banned by the prefecture drew nearly 3,000 people to Maurienne according to authorities, and 5,000 according to organizers. In early March 2025, Extinction Rebellion distributed 10,000 fake letters imitating TELT in Maurienne, warning of risks to drinking water. TELT denies the claims and files a complaint.

The opposition also comes from elected officials. In February 2026, the some 150 local elected officials gathered in the CEPURE (Collectif des élus pour l'utilisation du réseau existant) have appealed to the COI to demand an independent assessment. They rely on an administrative letter dated July 31, 2025, which they say confirms that no socio-economic assessment specific to the French access sections has been carried out. In July 2026, the green elected officials of the Auvergne-Rhône-Alpes regional council called for the tunnel works to be suspended.

Conversely, the project retains solid support: the Auvergne-Rhône-Alpes Region, numerous parliamentarians from all sides, the economic actors gathered in La Transalpine, and now once again the Métropole de Lyon, which announced its return to the association in September 2026. TELT also highlights an Ipsos BVA survey it commissioned in 2026 of 5,000 French and Italian people: 8 out of 10 would see it as a concrete opportunity.

Is the Lyon-Turin worth the effort?

Could the money have been better spent elsewhere?

Tens of billions of euros mobilized for an infrastructure whose French access sections still have no schedule, in a country where small lines are closing for lack of funding: the question inevitably arises. Would this money have produced faster climate and social benefits if it had been invested in the existing network? That is the central argument of opponents, and it deserves to be heard.

A European ambition worth taking seriously

But we also need to put the project back in its original context. The Lyon-Turin was born in post-Cold War Europe, an era when building bridges between nations was a priority. The grand corridor from Lisbonne to Budapest was the vision of an Europe brought closer together by movement and exchange. One can criticize the project's opacity, its delays and its costs, but this ambition also deserves to be taken seriously.

And if we truly want trucks off the Alpine roads and aviation to decline between Paris and Milan, one day we will need infrastructure up to the task. The debate is less about the principle than about the price, the timeline, the method, and everything that must surround a tunnel for it to truly serve its purpose.

The least that would be expected is to play fair on the ecological front: an updated carbon footprint, revised traffic forecasts, and an independent assessment of the French access sections, as demanded by the CEPURE elected officials or the ecologists of the Auvergne-Rhône-Alpes region. A project justified in the name of the climate should be the first to be accountable on that front.

A debate that goes beyond the tunnel itself

The Lyon-Turin is now part of a broader European movement. In November 2025, the European Commission presented a plan for high-speed rail by 2040, which aims, for example, to bring Paris-Rome down from 10h50 to 8h45 by train. The European Parliament backed it in October 2026, and MEPs are calling for more funding for major cross-border links in the next EU budget (2028-2034).

In France, the question of funding remains wide open. The framework bill on transport, adopted by the Senate in April 2026, provides for a future programming law that should set the funding trajectory for French access lines. But as of early November 2026, it still had not been definitively passed.

Finally, its defenders point to the fragility of current crossings: the landslide in the Maurienne valley cut the Paris-Milan line for 19 months (2023-2025), and the closure of the Mont-Blanc road tunnel for repairs in autumn 2025 sent most trucks back to the Fréjus. For its opponents, these episodes mainly show the urgency of maintaining the existing network.

What this story teaches us

Like the LGV Bordeaux-Toulouse, the Lyon-Turin shows that major infrastructure projects take on a life of their own. They are set in a specific context, weather crises, and change justification along the way. And once launched, they become almost impossible to stop, even when reasons to question them pile up. This is what's known as the sunk cost fallacy.

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Key takeaways

The Lyon-Turin is a 57.5 km tunnel under Mont Cenis, set to become the world's longest base rail tunnel, at the heart of a 270 km line between Lyon and Turin. Its cost reaches €11.1 billion for the tunnel alone, and around €26 to 30 billion with the access lines. Announced for 2015, then 2030, it is now expected in 2033, with no timetable for the French access lines. Its benefits for travelers are a consensus (Paris-Milan in a little over 4 hours), but its value for freight will depend on a real modal shift policy, like in Switzerland. But its ecological cost remains heavy and poorly documented: dried-up springs in the Maurienne, farmland paved over, and a carbon debt the European Court of Auditors estimates at 25 to 50 years of service. A project justified by the climate will have to prove it with updated, public figures. Stay tuned…

Written by Sophie Renassia

Issue du monde de la communication et des médias, Sophie est Responsable éditoriale chez HOURRAIL ! depuis août 2024. Elle est notamment derrière le contenu éditorial du site ainsi que La Locomissive (de l'inspiration voyage bas carbone et des bons plans, un jeudi sur deux, gratuitement dans ta boîte mail !).

Convaincue que les changements d’habitude passent par la transformation de nos imaginaires, elle s’attache à montrer qu’il est possible de voyager autrement, de manière plus consciente, plus lente et plus joyeuse. Son objectif : rendre le slow travel accessible à toutes et tous, à travers des astuces, des décryptages et surtout, de nouveaux récits.

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