NEW TURIN-LYON LINE

The Italian-French rail link at the heart of the TEN-T Mediterranean Corridor

The cross-border section

The heart of the project is the cross-border section, which stretches for 65 km between Saint-Jean-de-Maurienne, in France, and Susa/Bussoleno, in Italy. The route crosses the Alps via the Mont Cenis Base Tunnel, excavated beneath a rock overburden of up to 2,200 metres, in a mountainous environment characterised by highly complex geological conditions. The construction of the infrastructure therefore requires the use of state-of-the-art technology and high-level engineering solutions, in line with the most stringent safety, reliability and environmental sustainability standards.

The Mont Cenis Base Tunnel

The centrepiece of the new line is the Mont Cenis Base Tunnel, set to become the world’s longest railway tunnel. The tunnel, a twin-tube, single-track structure, extends for a total length of 57.5 km, of which 45 km in France and 12.5 km in Italy. The tunnel is one of the most impressive underground structures ever built in Europe, set to significantly transform transalpine rail links and promote a modal shift towards more sustainable transport systems.

The overall project entails the construction of tunnels extending for approximately 162 km, consisting of twin parallel tubes spaced between 30 and 50 metres apart and connected by cross-passages every 333 metres, for a total of 204 cross-passages. The system is completed by four access shafts, three surface-connected safe areas, and four ventilation shafts approximately 500 metres deep. Excavation work is carried out mainly using Tunnel Boring Machines, with seven TBMs in operation simultaneously.

Works in the Piana di Susa

The works on the new Turin–Lyon Line are complemented by above-ground works in the Piana di Susa area, including the Susa International Station, and the interconnection tunnels to the legacy line at Bussoleno. Here too, FS Engineering acts as the lead partner in the consortium with ARX and Systra.

The role of FS Engineering

FS Engineering, in a consortium with the international companies Systra France, ARX, Pini Group and SETEC, has been involved for years in the design work for the Turin–Lyon line. Winning the relevant tender, the company was commissioned by the binational project promoter TELT – Tunnel Euralpin Lyon Turin to act as project manager for two of the four operational lots of the Base Tunnel, one on the French side and one on the Italian side.

In the case of the above-ground works in the Piana di Susa area, FS Engineering, alongside ARX and Systra, leads the two operational construction sites, coordinating both the project management and the high-level supervision, with regard to the works under delegated procurement and the interference resolution.

Overall, the company is responsible for overseeing in excess of 60 per cent of the total works, confirming its key role in one of Europe’s most significant infrastructure projects.

Operational construction sites

On the French side, the S2IP Joint Venture, led by SETEC and comprising FS Engineering, Systra France and Pini Group, is responsible for Operational Construction Site CO6-7, the largest section of the entire base tunnel. The project involves the construction of approximately 27 km of twin-tube tunnel, including a complex safety system comprising interconnected tunnels linked to the outside, as well as logistics infrastructure dedicated to the assembly and handling of the three TBMs being used.

On the Italian side, the IS2P Joint Venture, led by FS Engineering and comprising SETEC, Systra France and Pini Group, is responsible for Construction Site CO3-4, which involves the construction of approximately 12 km of twin-tube tunnel. The worksite is supported by a complex system of logistics tunnels to assist with both conventional and mechanised excavation, as well as the management and storage of excavated material, with particular attention paid to the spoil resulting from the so-called ‘green stones’.

Also on the Italian side, the ISP Joint Venture, led by FS Engineering with the participation of ARX and Systra, is responsible for works management and overall supervision of works for Operational Construction Sites CO1 and CO2. The first Operational Site involves the construction, using conventional excavation methods, of the interconnecting tunnels at Bussoleno; the second comprises the above-ground works at Piana di Susa (line embankments, railway bridge over the Dora Riparia, noise barriers, bank protection works, environmental restoration works, etc., as well as the Susa International Station). FS Engineering’s responsibilities are further complemented by the coordination, through its role as high-level supervisor of works commissioned by TELT (on behalf of the clients SITAF and RFI), of the relocation of interfering infrastructure, and the resolution of all interferences affecting the new Turin–Lyon line in the Piana di Susa area.

Design and construction challenges

The construction of the Turin–Lyon line involves managing a complex technical, regulatory and organisational framework, characterised by the coordination of an international team and by operations in particularly challenging geological conditions. A key role is played by construction site management, which is committed to ensuring high standards of safety and efficiency, alongside the management of environmental issues through constant dialogue with the relevant authorities.

The project also utilises advanced supervision and quality control systems, supported by process digitalisation and sophisticated document management tools for continuous monitoring.

Objectives and benefits

The project aims to reduce road traffic between Italy and France and promote alternative modes of transport to road freight, against a backdrop of significant growth in transalpine freight traffic over recent decades. The new infrastructure will also foster the development of trade along the Mediterranean Corridor, contributing to the expansion of the Turin rail hub for freight and the improvement of passenger services, with benefits for urban mobility and airport connections.

Preparatory works, which began in 2012, led to the construction of approximately 10 km of tunnels and were completed between 2017 and 2019. Construction work subsequently resumed between 2021 and 2022, with timetables varying according to the individual contract lots. The Base Tunnel is currently scheduled for completion by 2032, marking a key milestone towards a more integrated, efficient and sustainable European transport system.