Gotthard Base Tunnel

The Gotthard Base Tunnel is a 57 km twin-tube railway tunnel under the Swiss Alps, running from Erstfeld in the canton of Uri to Bodio in the canton of Ticino, and it is the longest and most deeply set railway tunnel in the world, with rock overburden (rock and soil lying above a tunnel) reaching 2,300 m.^{1 • 2} Opened ceremonially on 1 June 2016 and in scheduled service since 11 December 2016, it carries passenger and freight trains and, together with the 15 km Ceneri Base Tunnel to the south, provides a virtually flat railway across Switzerland.^{3 • 4}

Why a base tunnel: the Alpine bottleneck

The idea of a flat tunnel under the Gotthard was sketched by engineer Carl Eduard Gruner in 1947.²

Swiss voters approved the project in a 1992 referendum on the government's resolution to construct the Swiss Rail Link through the Alps.^{2 • 6} Financing followed in a second referendum, when a 63.5% "yes" vote created the FinöV fund for public-transport infrastructure, worth 30 billion CHF.³

Design and route

The tunnel consists of two parallel single-track tubes with a diameter varying from approximately 8.80 to 9.50 m, linked by cross passages approximately every 300 m.³ The alignment keeps gradients low: the highest point of the track lies at 550 m above sea level.¹

The Gotthard Base Tunnel, together with the 35 km Lötschberg Base Tunnel (in full operation since December 2007), constitutes the NRLA.³

Construction: how 57 km of rock was excavated

Excavation took place from the portals as well as from three intermediate construction adits at Amsteg, Sedrun, and Faido.³ About 80% of the two main tubes were bored by tunnel boring machines and the remaining 20% by blasting.¹ The excavation produced 28.2 million tonnes of material.¹ Not counting exploratory work, construction took 17 years.¹

The hardest ground was in the Sedrun section, where poor rock of low strength with squeezing properties lay under an 800 m thick overburden.⁷ The support solution, adapted from mining practice, used yielding TH-steel ribs that allow controlled deformation, combined with intensive radial anchoring by self-drilling steel rock bolts. Average cross-section deformation reached 25 cm, and asymmetric deformation reached 85 cm.⁷

By the numbers

The effective total cost of the Gotthard Base Tunnel was CHF 12.2 billion, equivalent to CHF 9.7 billion at 1998 prices excluding VAT increases and construction interest.¹

The tunnel's credit rose from the original 6.3 billion CHF to 9.9 billion CHF (1998 price level), a 53% increase without inflation. Almost half of the extra costs came from variations ordered by the Swiss Federal Office of Transport (FOT), which aimed to deliver a tunnel with state-of-the-art safety measures and technology; ground risks accounted for only 9% of the increase, about a sixth of the total.³ Tunnel capacity is up to 260 freight trains and 65 passenger trains per day, with timetabled speeds of 100 km/h for freight and up to 200 km/h for passenger trains.¹

How the numbers compare

The 2,300 m of rock overburden is what sets the Gotthard apart.¹ Combined with the 15 km Ceneri Base Tunnel to the south, the Gotthard provides a virtually flat railway across Switzerland.⁴ The practical result is visible in journey times: a direct train from Zurich reaches Milan in 3 hours 17 minutes, against more than four hours ten years earlier.⁵ The Lötschberg Base Tunnel, at 35 km, together with the Gotthard Base Tunnel constitutes the NRLA.³

Opening and role in the network

The tunnel was opened with a ceremony on 1 June 2016, establishing the record as the world's longest railway tunnel, and entered scheduled operation with Swiss Federal Railways on 11 December 2016.³ AlpTransit Gotthard AG (ATG), a subsidiary of SBB, built the tunnel on behalf of the Federal Government on the geotechnically favored Erstfeld–Bodio route; ATG was also responsible for the 15 km Ceneri Base Tunnel.^{2 • 8}

Operating a tunnel of this length imposes its own regime. One tube is closed for three nights each time maintenance work is carried out. SBB prepared around 3,900 staff for the particular challenges of working in the Gotthard Base Tunnel.⁸

Recent developments

One of the two tubes remained closed for over a year; the tunnel returned to full normal service on 2 September 2024.⁵

Traffic through the tunnel has grown since opening even as the wider freight picture has weakened. Total freight rose from 15.3 million tonnes in 2015 to 17.9 million tonnes in 2024, and 69% of Swiss transalpine rail freight passed through the Gotthard in 2024, with the Simplon route carrying the remaining 31%.⁵ Daily rail passengers through the Gotthard nearly doubled from 9,000 in 2015 to 16,400 in 2025, and in 2025 an average of 155 trains ran daily, 66 passenger and 89 freight, against 174 trains through the old mountain tunnel ten years earlier.⁵

References

1. The Gotthard history (Gottardo 2016 official booklet), AlpTransit Gotthard AG. https://www.alptransit-portal.ch/Storages/User/Meilensteine/Pin_051/Dokumente_051/Gottardo_2016_Booklet_RZ_GzD_0505_ENG_WEB.pdf
2. Gotthard Base Tunnel, Encyclopaedia Britannica. https://www.britannica.com/topic/Gotthard-Base-Tunnel
3. Risk, Contract Management, and Financing of the Gotthard Base Tunnel in Switzerland, Engineering. https://www.engineering.org.cn/engi/EN/10.1016/j.eng.2019.04.001
4. Gotthard base tunnel, Civil Engineering (ICE). https://www.icevirtuallibrary.com/doi/10.1680/cien.14.00001
5. The Gotthard Base Tunnel ten years on, SWI swissinfo.ch. https://www.swissinfo.ch/eng/swiss-democracy/the-gotthard-base-tunnel-ten-years-on/91672319
6. Gotthard tunnel: World's longest and deepest rail tunnel opens in Switzerland, BBC News. https://www.bbc.com/news/world-europe-36423250
7. Gotthard Base Tunnel, Geotechnik Schweiz. https://geotechnikschweiz.ch/en/gotthard-base-tunnel-2/
8. The new Gotthard Tunnel – Switzerland through and through, Rhine-Alpine Corridor brochure. https://www.corridor-rhine-alpine.eu/files/pdf/Brochure_Gotthard_Basetunnel.pdf

Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Rail transport › Rail lines and infrastructure › Railway tunnels

Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Sep 30, 2026

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