2 May 2025 is set to be remembered as a historic date in the construction of the Brenner base railway tunnel. The last of the mechanical boring machines still in operation on the Italian side has completed excavation of the western tunnel. The other TBM had already finished digging and lining the parallel eastern tube back in March 2023. At this stage, all the main tunnels extending underground from Fortezza to the Italian-Austrian border—covering a distance of 44 kilometres—have been fully excavated and lined with concrete segments.
Furthermore, the Mules construction site, where the boring machine “Flavia” completed its task, is the most significant section of the entire Brenner base tunnel project. It spans nearly 40 kilometres and was awarded to a consortium led by Webuild for just under one billion euros. The Italian-side tunnels are now ready for the next phase involving finishing works, track installation and the setup of all systems.
While Italian workers can celebrate the completion of the major structural works, geological challenges and bureaucratic hurdles have slowed progress on the Austrian side. In the two main active sections—Sill-Pfons and Brenner—just over 19 kilometres of the main tunnels still need to be excavated out of a total of 50, excluding cross-passages and junctions. Work will therefore continue for several more years, with final excavation and lining expected between 2028 and 2029.
The Brenner base tunnel, measuring 55 kilometres in length and 64 when including the connection with the Innsbruck freight bypass, is the most significant and central component of the new high-capacity railway corridor between Verona and Munich. Equally crucial, however, are the access routes both from Italy and from Innsbruck towards the German border, to ensure maximum capacity and to bypass bottlenecks or critical sections. For this reason, certain segments deemed priorities have been advanced first, pending full duplication of the line.
In Italy, aligned with the timeline for completing the Brenner base tunnel, work has begun on the section between Fortezza (the southern portal) and Ponte Gardena, as well as on the Trento freight bypass. Further interventions will follow at the Bolzano and Verona nodes. Among these, the Fortezza-Ponte Gardena segment is the most significant, as it bypasses a particularly steep stretch on the historic line with gradients of 22 per mille. Awarded in June 2021 to Webuild and Implenia Construction for 1.16 billion euros, it entails seven years of construction and the creation of 22.5 kilometres of new line, mostly in tunnel. The worksites are currently active in creating the access shafts to the tunnels. In June 2024, construction also began on the southern entrance of the Trento freight bypass, where four tunnel boring machines will be used to excavate the 11 kilometres of double tunnel along a 13-kilometre variant. The works are being carried out by the Tridentum consortium led by Webuild, under a 1.3 billion euro contract.
And what about Austria? Unlike the only partially justified delays affecting the excavation of the Brenner base tunnel, the outlook for the northern access route is far more favourable, as Austria acted with remarkable foresight. After building the Innsbruck freight bypass in 1994, the Austrian railway operator ÖBB opened a 40-kilometre stretch in the Lower Inn Valley to traffic in 2012, from the northern portal of the Innsbruck bypass to Radfeld-Kundl, just south of Wörgl. By 2023, work had moved into the operational phase on the next section, from Radfeld to Schaftenau, just a few kilometres from Kufstein at the Austrian-German border.
Currently, efforts are focused on gaining full geological understanding of this particularly complex stretch, with pilot tunnels serving as the basis for the final alignment. In the cross-border Kufstein/Kiefersfelden area, environmental impact assessment surveys are under way. Simultaneously, ÖBB is working closely with German railway operator DB to finalise the technical design of the over-13-kilometre-long border tunnel.
Piermario Curti Sacchi
