The Turin–Lyon high-speed railway is an international rail line under construction between the cities of Turin and Lyon which will link the Italian and French high-speed rail networks. Nuova linea Torino-Lione parte comune tratta italiana – Progetto in variante – Studio d'impatto ambientale – sintesi non tecnica 9-7-2010 (document PP2 C3C TS3 0105A AP NOT) It will be long, of which over will be tunnelled. The core of the project is its 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, with some of the cost increase stemming from replacing the initially planned single-tube design by a double-tube design required by new stricter safety regulations.
Like the Swiss NRLA project, the line has twin aims of transferring freight traffic across the Alps from trucks to rail to reduce emissions and 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 (and in the title of this page), 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 (both by motorway and by rail) 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.Quaderno 1 2007, p. 4. The work of the commission between 2007 and 2009 was summarized into seven papers (Quaderni). 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 high-altitude (maximum tunnel altitude ) Fréjus Rail Tunnel.Quaderno 1 2007, p. 17. 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.Quaderno 1 – p. 16. 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 3.0%, 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 (Frejus tunnel and high valley section) Bussoleno–Avigliana (low valley section) Avigliana–Turin (metropolitan section) Turin node (urban section) The first section comprises the Fréjus tunnel and its approaches on both sides. Its high elevation (), sharp curves, steep gradients, and low tunnel ceilings make this section the bottleneck on the overall capacity of the line. A 2007 study calculated a maximum capacity of 226 trains/day, 350 days/year, under the safety regulations applicable at the time.Quaderno 1 2007, p. 30. The study, using the CAPRES model,CAPacité des RESéaux ferroviaires, Rivier, École polytechnique fédérale de Lausanne foresaw a maximum traffic of 180 freight trains per day, which had to be lowered to about 150 freight trains per day due to logistical inefficiency (the traffic flows between the two countries are asymmetric). A similar analysis for the full year led to a total of about 260 peak days per year.Quaderno 1 2007, p. 31. These conditions defined a maximum transport capacity per year of about 20 million tonnes when accounting for inefficiencies, and an absolute limit of about 32 million in "perfect" conditions.Quaderno 1 2007, p. 32.
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.Quaderno 1 2007, pp. 33–34. In 2007, the conventional line was used for only one-third of this calculated total capacity.Quaderno 1 2007, p. 35. Data are from 2007, while capacity was reduced by the 2007–10 modernization work. This low use level was in part because restrictions such as an unusually low maximum allowable train height and the very steep gradients (2.6–3.0%) 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-kilometre-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 (in million tons per year) of the future freight traffic on both the Frejus and Mont-Blanc corridors, from an analysis of then current data and macroeconomic predictions:Quaderno 2 2007, p. 18. Without the new line200420252030Annual growth 2004–2030 Alps – Total144.0264.5293.42.8% Alps – Rail48.097.7112.53.3% Modane corridor – Total28.558.163.83.1% Modane corridor – Rail6.515.816.43.6% With the new line200420252030Annual growth 2004–2030 Alps – Total144.0264.5293.42.8% Alps – Rail48.0111.4130.73.9% Modane corridor – Total28.563.576.53.9% Modane corridor – Rail6.529.539.47.2% Heavy vehicles (thousand per year)200420252030Annual growth 2004–2030 Without the new line1,4852,7913,1212.9% With the new line1,4852,2442,4471.9%
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 (e.g. the Channel tunnel) and underestimates (e.g. the TGV Est). 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 (due to reduced energy use thanks to a much flatter profile, but without necessarily taking into account the full construction cost of the new line), they propose to increase rail traffic by coupling additional renovation of the existing rail infrastructure with sufficiently high financial incentives for rail transport or sufficiently heavy tolls and taxes on road transport. The political realism of such taxes is questionable, as the French government demonstrated in 2013 when it withdrew a much smaller trucking ecotax when faced by extensive riots initiated by the trucking industry 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 brand-new line will also meet 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.Quaderno 2 2007, pp. 36-39.
New railway line
The new railway line will have a maximum gradient of 1.25%, compared to 3.0% 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 (TELT SAS), a joint venture of Rete Ferroviaria Italiana (RFI) 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 (Susa valley) and Turin is under RFI.
Due to the asymmetry of the Alps, which peak much closer to the Northern Italy plain than to flat terrain in France, the 140 km French section is three times longer than its 46.7 km Italian counterpart.
French section The French section of the new line is planned with eventually separate paths for passengers and freight between Lyon and the Maurienne valley. The passenger line will link the LGV Sud-Est (through a connection South of Gare de Lyon Saint-Exupéry) and the central Lyon stations to both Italy and Chambéry. It will connect near Chambéry to the Annecy via Aix les Bains and the Bourg Saint-Maurice via Albertville lines. The time gain from Paris or Lyon to Aix-les-Bains or Chambéry will be almost 45 minutes, and almost an hour to Annecy. The line may also be used to offload the saturated Lyon–Grenoble line from its TGV traffic. This would remove traffic at mismatched speeds, and therefore would free many more train paths for much needed additional local trains than the number of TGVs shifted to the new line.