The Brenner Base Tunnel (BBT), set to become the world’s longest underground rail link, has marked a major milestone with the first physical connection between Italy and Austria. Engineers broke through a 400-metre stretch of rock in the exploratory tunnel in September 2025, linking the two countries beneath the Brenner Pass at a depth of around 800 metres.
The connection represents years of excavation work and highlights the precision of cross-border engineering. The exploratory tunnel runs 12 metres beneath the alignment of the future twin rail tunnels and plays a crucial role in surveying geological conditions, aiding safety and maintenance once services begin.
Europe’s longest rail tunnel
When complete, the BBT will extend 64 kilometres between Fortezza in Italy’s South Tyrol and Innsbruck in Austria, surpassing Switzerland’s Gotthard Base Tunnel to become the longest in the world. Including the Innsbruck bypass, the overall system will reach 64 kilometres.
The project is a core part of the Scandinavian–Mediterranean corridor, one of the EU’s priority transport routes. By creating a high-speed rail link beneath the Alps, the tunnel will enable more freight and passenger traffic to move from road to rail. Travel time between Innsbruck and Fortezza will fall from two hours to just 25 minutes, with wider impacts on journeys between Munich, Verona and beyond.
The Brenner corridor is one of Europe’s busiest freight routes, with millions of tonnes moved by lorry each year. The BBT will help shift this traffic to rail, cutting CO₂ emissions by an estimated 1.5 million tonnes annually. It is also expected to reduce congestion, noise and pollution in Alpine valleys.
Passenger services will benefit from faster and more reliable travel, while the construction phase continues to support around 4,000 jobs across Austria and Italy. Contractors have deployed advanced tunnel boring machines (TBMs), capable of excavating up to 20 metres per day.
International cooperation
The project is managed by BBT SE, a company jointly owned by Austria and Italy, with significant funding from the European Union. The EU views the BBT as essential to its climate and connectivity goals and has supported it through the Connecting Europe Facility.
The successful breakthrough required teams from both countries to align excavation fronts with millimetre precision, demonstrating the value of international cooperation in major infrastructure.
Next steps
More than half of the tunnel system has now been excavated, though significant work remains to complete the twin main tubes. Geological challenges continue to shape progress, including fractured rock and water inflows.
Once open in the early 2030s, the BBT will accommodate around 400 trains a day. A single freight train through the tunnel could replace up to 150 lorries on Alpine roads, while passenger trains will run at speeds of up to 250 km/h.
BBT: A European symbol
The first connection between Italy and Austria is both an engineering achievement and a symbol of integration. As BBT SE described it, the breakthrough demonstrates what can be achieved when nations and institutions work together to deliver transformative infrastructure.
The Brenner Base Tunnel will not only bridge two sides of the Alps but also connect regions, economies and people across Europe, advancing both sustainable transport and cross-border mobility.
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