Projects & backgrounds

BLS is upgrading the Lötschberg Base Tunnel

The Lötschberg Base Tunnel is the centrepiece of the BLS infrastructure and a central element of the NRLA, the New Rail Link through the Alps. BLS upgrades the Tunnel. This will put in place the prerequisites for a half-hourly Intercity service between Bern and Valais. And freight trains will therefore travel more frequently through the Base Tunnel instead of using the Lötschberg mountain line, thus increasing productivity.

Since the Lötschberg Base Tunnel was first commissioned in 2007, it has been impossible to imagine Swiss transport infrastructure without it. Whether commuters on their way from Valais to Berne, holidaymakers travelling from German-speaking Switzerland to the Valais mountains or business travellers making the journey to northern Italy, the tunnel reduces the journey time for them all. Freight, too, passes through the Lötschberg section of what is termed the "Rhine Alpine Corridor" at all hours of the day and night.

7 Kilometer up to the double track extension

The Lötschberg Base Tunnel is now on the cusp of full capacity. More and more passenger and freight trains are travelling through the approximately 35 kilometre-long tunnel. The main challenge: only around 40% of the line through the base tunnel is twin track. A second 14-kilometre tunnel tube has indeed been cut, but it has not yet been equipped for railway operation. A further seven kilometres are still to be cut through, so that trains can travel continuously through the tunnel on two tracks.

Partial or full upgrade? The Swiss parliament will decide

In 2019, the Swiss parliament gave the green light for partially upgrading the Base Tunnel: BLS has the task of upgrading the railway infrastructure within the existing unfinished tunnel bore between Ferden and Mitholz. Major construction work is required in order to connect the new tunnel section to the existing single-track section at Mitholz. For this purpose, the tunnel must be closed for eight months. Owing to this lengthy closure, the Swiss parliament has commissioned the Federal Council to once more review the full upgrade of the tunnel. This is why BLS is also continuing to plan the project for the full upgrade, so that both project versions are available at a comparable level of planning maturity by late-2022.

At that point, parliament will have the choice: it is scheduled to decide by early 2023 whether it wishes to adhere to the previously approved partial upgrade or whether the tunnel should be fully upgraded. Until this decision is made, BLS will not issue its invitation to tender for the primary construction work on the partial upgrade. Instead, from 2022 onwards the company will conduct certain preparatory tasks required for both versions. The partial-upgrade project is also open to public consultation in the summer of 2020. This means that BLS can speedily implement the partial upgrade if this is the version that parliament ends up choosing. Should parliament instead opt for a full upgrade, BLS will publish a project amendment for public consultation.

Partial extension means

  • In the existing unfinished tunnel bore, a concrete floor will be built, the vault sealed with a special kind of sheeting and then clad with an inner tube of concrete.
  • Fitting the existing basic tunnel tube with railway equipment between Ferden and Mitholz:
    • a slab track will be built in. Instead of traditional ballast, the sleepers will be laid on a fixed concrete bed. In addition, catenary wires are to be installed along the entire length of the new rail tunnel.
    • Other technical equipment, such as ventilation and water systems, high-voltage plants and equipment, rail tunnel portals, radio equipment, lighting and safety equipment will be extended and adapted.
    • Installation of high-speed points in Mitholz, connecting the newly upgraded tunnel tube with the remaining single-track line. This set of points is 160 metres long, so that trains travelling at a speed of 180 kph (112 mph) can run through.
    • Installation of three additional sets of points in Ferden. This will provide the option of shifting maintenance work from one tunnel tube to another.
  • The second, existing, unfinished tunnel tube of the Engtsligen Tunnel between Frutigen and Wengy-Ey will also be fitted out with rail equipment and connected to the existing line.

Key facts and figures

Construction period

  • 2026 - 2034


  • Partial upgrade: approx. CHF 973,5 million

Advantages of an expansion

Advanteages of a partial upgrade

  • This will make a half-hourly long-distance service between the Cantons of Bern and Valais possible
  • It will reduce production costs associated with freight traffic, because trains will no longer need to take the significantly longer mountain route.This would make rail freight more competitive compared to road haulage and support implementation of the Federal Government's policy of transferring heavy goods traffic from road to rail.
  • The Alpine region continues to present topographical difficulties. Alternative options are important. The Lötschberg and Gotthard routes therefore offer complementary solutions.
  • The mountain line will be relieved of freight traffic. This will benefit both the environmentally-sensitive Alpine region and local tourism.

Advantages of a full upgrade

  • The full upgrade of the Base Tunnel doesn’t require a complete closure of the tunnel. This avoids a negative economic impact.
  • The direct full upgrade is cheaper than the phased expansion and costs tax-payers less in the long term.
  • The full upgrade will increase timetable reliability and flexibility throughout the entire Swiss rail network.
  • The tunnel can be refurbished without disrupting rail operations.

Key figures

  • 500'000: This is the number of trains travelling through the Base Tunnel (mid 2022).
  • A total of 50 passenger trains and up to 80 freight trains use the Base Tunnel every day. It is therefore operating at an average of 80% capacity – higher capacity utilisation of the rail line can scarcely be achieved if seasonal fluctuations are taken into consideration.
  • The base tunnel is 34.6 kilometres long. Of those, however, only 14 kilometres currently consist of double-track lines. Structural work is still being carried out on parts of the western tube, while another section has not yet been tunnelled.
  • In 2021, 27,9 million gross tonnes of freight were transported on the Lötschberg axis (Base Tunnel and mountain line). The market share of the Lötschberg axis in transalpine freight transport through Switzerland was therefore 41 per cent.


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Nothaltestelle Ferden
Lötschberg Base Tunnel

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Frutigen Intervention & Maintenance Centre
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Nothaltestelle Ferden
Nothaltestelle Ferden
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