4 October 2018IDM

World’s longest tunnel under construction in the heart of Europe

Upon completion in 2027, the 64-kilometre Brenner Base Tunnel will connect Italy with Austria, providing an important transport link between Northern and Southern Europe. More than 1,000 people from 13 EU countries are working on the project, with almost half of the companies involved based in the region.

In less than ten years, it will be the longest tunnel in the world. Stretching 64 kilometres between Fortezza and Innsbruck, it will not only create a better link between Italy and Austria, but between Northern and Southern Europe as well. The project will bring these regions much closer together, with South Tyrol acting as a strategic link. We are talking about the visionary Brenner Base Tunnel (BBT), one of the most ambitious, forward-looking projects of our time. “The tunnel is at the heart of the Scandinavian-Mediterranean corridor running from Helsinki to Valletta in Malta. Completing it is one of the corridor’s priorities. It will strengthen the Italian-Austrian connection and have a positive impact on all European countries, especially those directly affected by the project,” states Raffaele Zurlo, CEO of BBT SE, the company supervising the construction. 

Seven construction sites have been set up in Austria and Italy

Since the BBT is a transnational project, a Societas Europaea was founded to manage it. This is a special type of company provided for by European law to run projects of this kind. Half of the shares in the company are held by Austria and half by Italy. The Austrian shareholder is ÖBB Infrastruktur AG, the operator of the Austrian railway network, while the Italian shareholder is Tunnel Ferroviario del Brennero Holding AG, which in turn is owned by the Italian public railway company RFI (87.92%)[C1] , the Autonomous Province of Bolzano, the Autonomous Province of Trento and the Province of Verona. 

At an altitude of 1,371 metres, the Brennero/Brenner Pass is the lowest pass in the Alps and the future tunnel will run underneath it at an elevation of 794 metres. Work is currently underway at seven construction sites in Italy and Austria. It is envisaged that the completed tunnel will mainly be used to transport goods, although it will also convey passengers to a lesser extent. Compared to the current route, the section between Fortezza and Innsbruck will shorten the travel distance from 75 km to 55 km and the gradient will be reduced significantly, from the current maximum of 26‰ to just 6.7‰. This means that passenger trains will be able to travel at a speed of 250 km/h and freight trains at 160 km/h. In addition to the tunnel entrances and exits in Fortezza and Innsbruck, four lateral access tunnels will also be constructed to connect the railway and exploratory tunnels to the outside – three in Austria (Ampass, Ahrental, Wolf) and one in Italy (Campo di Trens, South Tyrol). 

Use of special techniques such as ground freezing and jet grouting

Our journey begins at the Isarco river underpass near Fortezza, which is the southernmost section of the Brenner Base Tunnel and is being constructed for a total of 303 million euros. The contract to construct this section, which will link the tunnel with the existing Brenner railway line and Fortezza station, was awarded to the cooperative RTI Salini-Impregilo S.p.A., Strabag AG, Strabag S.p.A., Consorzio Integra and Collini Lavori S.p.A. A total of 4.2 kilometres of main tunnels and 1.5 kilometres of connecting tunnels will be constructed to connect the BBT to the existing railway line. “Around 350 people are working on this construction lot alone, which involves digging four tunnels just five metres under the river bed. Due to this very low construction depth, we needed to use special techniques such as ground freezing and jet grouting. We are reinforcing the ground, which is mainly composed of loose fluvioglacial deposits, so that we can make it virtually impermeable,” explains engineer Stefano Torresani, project manager of the Isarco construction site. He adds that, in addition to the river, this section of the tunnel will pass under the A22 Brenner Autobahn motorway, the SS12 main road and the existing railway line. During the current construction phase, four shafts providing access to the excavation sites are also being constructed. Like the four planned tunnels, these have a diameter of 35 metres and a depth of 25 metres. 

Mules 2-3: a total of 65 kilometres of tunnels are being dug here

The next construction site is Mules 2-3, which currently employs around 600 people, although this figure is set to grow to more than 850 during peak periods. Work at this section has a budget of 993 million euros and the contract was awarded to a group of companies comprising Astaldi S.p.A., Ghella S.p.A., Oberosler Cav Pietro S.r.l., Cogeis S.p.A. and PAC S.p.A. Over the course of the seven-year construction period, almost 40 kilometres of tunnels and approximately 14 kilometres of exploratory tunnels are expected to be built here, including the emergency stop in Trens and its access tunnel and the bypasses. Mules 2-3 is the largest construction site in the Italian project area and stretches from the Isarco river underpass to the border with Austria. Taking into account all the work being conducted on the site, an impressive 65 kilometres of tunnels will be excavated by the end of 2023. At present, the tunnel is being driven at six excavation sites at the same time. Explosives are being used at three of these, while at the other three, tunnel boring machines with rotating cutter heads are chipping away at the rock. “Since using the first cutter head ten days ago, we have already bored through around 75 metres of rock, which is an average of 7.5 metres a day. We are planning to double this speed over the next month,” explains engineer Stefano Fuoco, site manager of the Mules 2-3 construction lot.

South Tyrolean or Tyrolean companies involved in almost 50% of tenders

From civil and geotechnical engineers to legal consultants and communications experts, a wide range of professionals are needed to construct the BBT

The figures reveal the truly impressive scale of the project. More than 1,000 people comprising manual workers, technicians, engineers, construction managers and geologists from 13 European countries are employed on the Italian construction sites and 82 of the planned 230 kilometres have already been excavated. The project costs amount to 8.4 billion euros and almost half of the tenders involve companies that are headquartered or have permanent business establishments in South Tyrol or Tyrol. “Although the tunnel is not due to be completed until 2027, it is already having an impact on the economy and job market,” confirms CEO Zurlo. “This is because the project requires a wide range of professionals – from civil and geotechnical engineers to legal consultants and communications experts. It is a mammoth undertaking that gives everyone involved the chance to gain once-in-a-lifetime experiences.” This is why various vocational training programmes have been launched within the framework of the “La buona Scuola” education reform introduced by Italian Law 107 alongside various initiatives and internship schemes with major European universities and schools. Students are also able to visit the BBT site while writing their degree or PhD theses. What’s more, open days are being organised for local residents, the most recent in September 2017 attracting almost 4,000 visitors. 

A total of around 400 million euros were saved in 2017

The figures relating to the project costs are positive too, with the planned investment costs having been revised downwards twice, creating total savings of around 400 million euros (2017 data). The resulting public money saved can now be used to fund other projects. Attention is also being paid to mitigating the impact of the Brenner Base Tunnel on the surrounding regions. “Compensatory measures costing 50 million euros have been planned for the areas affected by the project. Our aim is to reduce the impact on the environment to a minimum and for the construction sites to cause as little disruption as possible. Once the work is complete, everything will be returned to how it was before and, with the exception of one bridge, the structures built will all disappear,” assures Zurlo.

See how construction is progressing in virtual reality thanks to South Tyrolean start-up Realer

Anyone interested in following the progress of this unique project virtually and almost in real time has the chance to do so on a monitor set up by South Tyrolean start-up Realer in the BBT Infopoint in Fortezza. Everyone else can look forward to seeing the tunnel in use once it is opened in 2027. 



Fact sheet


1847: Italian engineer Giovanni Qualizza is the first to raise the idea of constructing a tunnel under the Brenner Pass 

1971: The UIC (International Union of Railways) commissions a feasibility study into the completion of a new Brenner railway line with a base tunnel 

1989: Three feasibility studies are drawn up that will go on to form the basis for further plans to build the Brenner Base Tunnel

1994: The European Union includes the Berlin-Naples corridor in its list of priority projects 

1999: Preliminary planning officially begins and plans are announced as final in 2002

2004: Italy and Austria sign a State Treaty to build the Brenner Base Tunnel

2007: Construction work begins in Italy

2009: Construction work begins in Austria


64: Length in kilometres of the tunnel connecting Fortezza with Innsbruck, including the Innsbruck bypass 

8.4 billion euros: The estimated total cost of the project, 50% of which is being covered by the European Union

400 million euros: Amount saved compared with the initial cost estimate

50 million euros: Funding for compensatory measures in South Tyrol

2027: Planned year of completion

1,000: Number of skilled workers employed on the construction sites 

4: Active construction sites, two in Italy and two in Austria

4: Lateral access tunnels

4.0‰–6.7‰: Envisaged longitudinal gradient

3: Cutting-edge tunnel boring machines used for the excavation work in South Tyrol

3,800: Number of visitors attending the open day held in September 2017

30%: Proportion of transalpine freight traffic that currently travels across the Brenner Pass