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Beneath the Alps: Brenner Base Tunnel Breakthrough Connects Italy and Austria

Sep, 25, 2025
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Authored by: TheCivilEngineer.org

*Breakthrough of the exploratory tunnel beneath the Alps. Source: Newsweek (image by Brenner Basistunnel BBT)*

The Brenner Base Tunnel (BBT), a major European infrastructure project, has reached a landmark breakthrough. For the first time, Italy and Austria are directly connected beneath the Alps through a continuous exploratory tunnel, marking a significant step toward the completion of what will become the world’s longest underground railway link.

At nearly 64 km including the Innsbruck bypass, the tunnel will cut passenger journey times between Fortezza and Innsbruck from 80 minutes to roughly 25 minutes. Running up to 1,400 m below the surface, the alignment provides an almost flat rail connection, enabling faster and more efficient freight and passenger flows across the Scandinavian–Mediterranean Corridor.

Excavation has faced demanding geology, requiring techniques such as nitrogen soil freezing to stabilize weak ground. On the Austrian side, tunnel boring machines (TBMs) have successfully traversed fault zones including the Viggar valley and the Werner zone, with several main breakthroughs achieved in 2025.

Overview of tunnelling work done in challenging alpine strata. Source: NCE

So far, approximately 87% of the project’s planned 230 km of underground works have been excavated. Once complete, the twin main tubes will accommodate longer, heavier trains, reducing reliance on road transport and alleviating pressure on alpine highways.

Beyond its transport role, the tunnel carries strategic importance for resilience. By shifting freight from road to rail, it contributes to decarbonisation targets and reduces environmental pressures in alpine valleys. It is also expected to improve transportation resilience, including during crises, by supporting faster movement of goods and people

The €10.5 billion project is jointly funded by Austria and Italy, with half of the cost supported by the European Union. Full completion is expected by 2032, making the Brenner Base Tunnel a key component in efforts toward sustainable mobility and improved European connectivity.

Sources: newcivilengineer.com, euractiv.com, webuildgroup.com