For the first time, Italy and Austria are directly linked beneath the Alps: engineers have completed a continuous exploratory tunnel of the Brenner Base Tunnel, a landmark step in construction of what will be the world’s longest underground railway connection.

A symbolic crossing of the newly connected tunnel took place at about 1,400m below the Brennero (Brenner), where a small delegation passed through the border inside the borehole. The breakthrough follows months of tunnelling from both sides of the frontier and comes after the Flavia tunnel boring machine (TBM) completed a more than 14km excavation from the Italian side to the Austrian border in spring 2025.

The Brenner Base Tunnel, which forms part of the Munich–Verona axis on the Trans‑European Transport Network’s Scandinavian–Mediterranean Corridor, will run for about 64km, including the Innsbruck railway bypass. Once finished it is intended to permit passenger trains to run at up to 250km/h and cut journey times between Fortezza (Franzensfeste) in Italy and Innsbruck in Austria from about 80 minutes to roughly 25 minutes.

Planners say the tunnel is a strategic piece of infrastructure to shift freight and passenger traffic from road to rail through the Alps, reducing emissions and noise in the sensitive alpine environment.

(NB: Graphic from 2022)

 Italian engineering group Webuild led the consortium that completed the Italian-side works on behalf of project client BBT SE. Webuild has overall responsibility for more than 50km of tunnel construction on the project, divided into four contracts. Two of those sections are already finished: the Isarco underpass at the southern end of the tunnel, near the Fortezza station, and Lot H33 Tulfes‑Pfons on the Austrian side. Webuild is also working on complementary upgrades for the Italian rail network – the Fortezza–Ponte Gardena line and a Trento bypass – which are intended to increase capacity and integrate the tunnel into national and trans‑European services.

Tunnelling through the Alps has demanded complex engineering. Webuild said it used techniques such as nitrogen soil freezing to stabilise ground conditions during excavation.

Credit: Webuild Image Library

On the Austrian side, contractors led by Implenia have also been contending with difficult geology: in August a TBM named Ida completed the first breakthrough of a main tunnel tube in the H41 Sill Gorge–Pfons lot, after boring about 8.4km of rock. Ida, which is roughly 160m long with a cutter head 10.4m in diameter, encountered several challenging fault zones – including the Viggar valley area and a thick “Werner” zone – which were traversed successfully in early 2025.

A second TBM, Lilia, is expected to complete the eastern main tunnel tube in the same construction lot in autumn 2025, which project managers say will finalise the TBM-driven excavation in that section.

When completed, the Brenner Base Tunnel is intended to improve freight and passenger flows along one of Europe’s busiest north‑south corridors and to contribute to the bloc’s decarbonisation targets by offering a faster, lower‑emission alternative to lorry and car traffic over the Alps.

Webuild chief executive Pietro Salini said: “We are proud to be able to contribute to the development of sustainable mobility in Europe with strategic projects like the Brenner Base Tunnel.”

“Today’s outcome is the fruit of the extraordinary work made possible by the commitment and expertise of Webuild Group’s people and the companies along the supply chain in facing one of world’s most complex engineering feats.

“We have excavated under the Alps, overcoming extreme geotechnical conditions thanks to the adoption of advanced technological solutions, all the while ensuring safety and sustainability at every stage. The tunnel that today joins Italy and Austria represents the skill of Italy’s infrastructure industry in building strategic projects for a greener future in mobility in Europe.”

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