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. It is intended to link the Italian and French high-speed rail networks and will be long. 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. At , that tunnel will be the longest rail tunnel in the world, ahead of the Gotthard Base Tunnel. The estimated total cost of the line is €25 billion, of which €8 billion is for the international section. The latter is the only part of the line where construction has started.

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 (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 line is therefore part instead of the TEN-T Trans-European conventional rail network within its "Mediterranean Corridor"—previously "Corridor 6". 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. 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.

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, 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 late 2022, the expected completion date for the base tunnel was 2032. Provided by Wikipedia