In less than 10 years, a huge tunnel will cut through the centre of the Alps to connect two major European countries and slash journey times by more than half. Huge boring machines will create a 57.5km (35.7mile) tunnel through the Alps to connect French and Italian high-speed rail networks and link Lyon with Turin.

The gargantuan Turin–Lyon high-speed railway will shave two hours from the 3-hour 47-minute train journey, which currently traverses the steep and winding Mont Cenis mountain to altitudes of around 1,300metres. At present, three locomotives have to haul the trains, and they also have to pass through the Fréjus Rail Tunnel, which doesn’t meet current safety standards.

Instead, the multi-billion-pound Mont Cenis base tunnel, also known as the Mont d’Ambin Base Tunnel, will enable trains to travel directly through the centre, with entry points at the Susa Valley in Piedmont and Maurienne in Savoie.

Freight trains will be able to carry heavier loads of cargo, while wider curves compared to the existing line will allow them to transit between the two countries at 100 km/h (62 mph).

It is hoped that air traffic will reduce as passengers opt for rail journeys, which could reduce air pollution. The multi-billion-pound collaboration is also hoped to reduce emissions on the roads, as freight companies opt for rail travel instead of lorries.

Once constructed, it will become the longest rail tunnel in the world, ahead of the 57.1 km (35.5 mi) Gotthard Base Tunnel in Switzerland, and that’s not even taking into account the difficulty of the project. At its deepest section, the overburden will be more than 2,200metres.

According to TELT’s project director Alexandre Heim, there are 14 different types of ground conditions along the tunnel route to add to the complexity, ranging from loose ground at the French side to challenging schist and gneiss formations between Modane and the Italian border, reports Off Site.

Unsurprisingly, it is coming at a major cost for both countries. The 270 km (170 mi) Turin–Lyon high-speed railway is estimated to cost €25billion (£21.8billion) in total. 

The 57.5km (35.7-mile) tunnel under the Alps is reported to take up a major portion of the entire project’s cost, estimated at around €11 billion in 2024.

France and Italy reached a mutual agreement nearly ten years ago in 2016 to begin construction on the tunnel, and it had been in the pipeline for years before that. 

Now, all four of the access tunnels, three in France and one in Italy, have been completed. The international tunnel is the only part of the line where construction has started. It is expected to be finished by 2033.