Turin–Lyon high-speed railway
The Turin–Lyon high-speed railway is an international rail line under construction between the cities of Turin and Lyon, which is intended to link the Italian and French high-speed rail networks. It will be long, of which over will be tunneled. The core of the project is its long international section, which will cross the Alps through the Mont d'Ambin Base Tunnel between the Susa Valley in Piedmont and Maurienne in Savoie. The total cost of the line was estimated in 2016 to €25 billion, of which €8 billion was for the international section. The latter was updated to €11 billion in 2024 once most contracts were signed.
Like the Swiss NRLA project, the line has twin aims of transferring freight traffic across the Alps from trucks to rail to reduce CO2 emissions as well as local air pollution and of providing faster passenger transport to reduce air traffic. The new line will considerably shorten the journey times, and its reduced gradients and much wider curves compared to the existing line will also allow heavy freight trains to transit between the two countries at and with much reduced energy costs. In spite of the name often used by media, the line is not high-speed under the definition used by the European Commission: its design speed of is 12% below the threshold used by the commission to define high-speed railways. The European Union funds 40% of the tunnel costs, and has indicated its willingness to increase its contribution to 55%, as well as to help fund its French accesses if those go beyond mere adaptations of the existing infrastructure.
The project has been criticized for its cost, because traffic was decreasing when the project was decided, for potential environmental risks during the construction of the tunnel, and because airplanes will still, after including time to and from the airport and through security, be slightly faster over the full Milan–Paris route, although not over shorter segments such as Paris–Turin or Milan–Lyon. A 2012 report by the French Court of Audit questioned the realism of the costs estimates and traffic forecasts. Opposition to the project is mostly organised under the loose banner of the No TAV movement.
The international section is the only part of the line where construction has started. Civil engineering work started in 2002 with the construction of access points and geological reconnaissance tunneling. A gallery tunneled between 2016 and 2019 from Saint-Martin-de-la-Porte towards Italy was presented as reconnaissance work because the project had not yet been formally approved, but it was dug at the position of the south tube of the tunnel and at its final diameter. It effectively represents the first 8% of the final tunnel length. As of mid-2025, the expected completion date for the international section was 2033.
Pre-construction studies
The merits of the new line were the subject of heated debate, primarily in Italy. After violent confrontations between opponents and police during a 2005 attempt to start reconnaissance work near Susa, Piedmont, an Italian governmental commission was set up in 2006 to study all the issues.The work of the commission between 2007 and 2009 was summarized into seven papers. An eighth summary paper focused on cost–benefit analysis was unveiled in June 2012.
Present high-altitude line
Since 1872, the Turin–Modane railway connects Turin with Lyon via the -long high-altitude Fréjus Rail Tunnel. This initially single-track line was doubled and electrified in the early 20th century, and the Italian side of the line was renovated between 1962 and 1984, and again between 2001 and 2011. This historical line has a low maximum allowed height, and its sharp curves force low speeds. Its very poor profile, with a maximum gradient of 30‰, requires doubling or tripling the locomotives of freight trains. The characteristics of the line vary widely along its length. The Osservatorio divides the international and Italian sides into four sections:- Modane–Bussoleno
- Bussoleno–Avigliana
- Avigliana–Turin
- Turin node
Additional traffic limitations stem from the impact of excessive train transit on the population living near the line. Some 60,000 people live within of the historical line, and would object to the noise from late-night transits. In 2007, the conventional line was used for only one-third of this calculated total capacity. This low use level was in part because restrictions such as an unusually low maximum allowable train height and the very steep gradients and sharp curves in its high valley sections discourage its use. A 2018 analysis, however, found the existing line close to saturation, largely because safety regulations now prohibit passenger and freight trains from crossing in a double-track single-tube tunnel. This very significantly reduces the maximum allowed capacity of the 13.7 km long Fréjus tunnel, which trains of one type must now fully cross before any train of the other type can be allowed in the other direction. The path of the historical line through the deep Maurienne valley is also exposed to rockfalls, and a major landslide in August 2023 forced its closure for a year and a half.
Traffic predictions on Frejus and Mont-Blanc corridors
The following table summarizes 2007 predictions of the future freight traffic on both the Frejus and Mont-Blanc corridors, from an analysis of then current data and macroeconomic predictions:| Without the new line | 2004 | 2025 | 2030 | Annual growth 2004–2030 |
| Alps – Total | 144.0 | 264.5 | 293.4 | 2.8% |
| Alps – Rail | 48.0 | 97.7 | 112.5 | 3.3% |
| Modane corridor – Total | 28.5 | 58.1 | 63.8 | 3.1% |
| Modane corridor – Rail | 6.5 | 15.8 | 16.4 | 3.6% |
| With the new line | 2004 | 2025 | 2030 | Annual growth 2004–2030 |
| Alps – Total | 144.0 | 264.5 | 293.4 | 2.8% |
| Alps – Rail | 48.0 | 111.4 | 130.7 | 3.9% |
| Modane corridor – Total | 28.5 | 63.5 | 76.5 | 3.9% |
| Modane corridor – Rail | 6.5 | 29.5 | 39.4 | 7.2% |
| Heavy vehicles | 2004 | 2025 | 2030 | Annual growth 2004–2030 |
| Without the new line | 1,485 | 2,791 | 3,121 | 2.9% |
| With the new line | 1,485 | 2,244 | 2,447 | 1.9% |
Promoters of the new line predict that it will about double rail traffic on the Modane corridor compared to the reference scenario. Traffic predictions of even the early traffic of major rail infrastructures are intrinsically uncertain, with well-known examples of overestimates, as well as underestimates. Some experts disagree with the necessity for a new line connecting France and Italy on the Modane corridor, quoting wide margins for increase in traffic on the old line. Rather than as a natural consequence of faster transit times and a lower price for freight shipping, they propose to increase rail traffic by coupling additional renovation of the existing rail infrastructure with sufficiently high financial incentives for rail transport and/or sufficiently heavy tolls and taxes on road transport. The political realism of such taxes is questionable, as France demonstrated in 2013 when its government withdrew a much smaller trucking ecotax after the trucking industry initiated extensive riots as part of the Bonnets Rouges movement. A 2018 study made this specific controversy much less relevant by finding that the existing line actually is close to saturation. This is primarily because updated safety regulations on train crossings in single-tube tunnels have significantly reduced its maximum allowed capacity. The construction of a brand-new line will also allow higher safety standards, and it will make the older infrastructure fully available for regional and suburban services, which is an important consideration near the congested Turin node.
New railway line
The new railway line will have a maximum gradient of 12.5‰, compared to 30‰ for the old line, a maximum altitude of instead of, and much wider curves. This will allow heavy freight trains to transit at and passenger trains at a top speed of, while also sharply reducing the energy used. The construction of the full higher-speed line will cut passenger travel time from Milan to Paris from seven hours to four, becoming time-competitive with plane travel for city-centre to city-centre travel. The line is divided into three sections constructed under separate managements:- the international section between Saint-Jean-de-Maurienne in Savoie and Bussoleno includes the Mont d'Ambin Base Tunnel. Its ongoing construction is managed by Tunnel Euralpin Lyon Turin, a joint venture of Rete Ferroviaria Italiana and SNCF that replaced Lyon Turin Ferroviaire;
- the French section between Saint-Jean-de-Maurienne and the outskirts of Lyon will be built under SNCF Réseau management;
- the Italian section between Bussoleno and Turin is under RFI.