The Brenner Base Tunnel (BBT): shifting Alpine traffic from road to rail

The Brenner Base Tunnel, located between Austria and Italy, is celebrating today in the Pfons-Brenner site (Austria) the start of the excavation of the two Tunnel Boring Machines (TBMs), named Wilma and Olga. These are the last two TBMs entering into service, for achieving the BBT tunnelling. Representatives of the European Commission and CINEA attended the ceremony to celebrate this important milestone made possible thanks to EU funding.

The Brenner Pass is one of Europe’s busiest mountain crossings used for freight transport. Each year, more than 2.5 million trucks, 14 million vehicles, and 50 million tonnes of goods cross the Alpine pass. The new Brenner Base railway tunnel, co-funded with EUR2.3 billion for four Actions from the CEF Transport programme, aims to ease congestion on the Munich-Verona route, which is part of the Scandinavian-Mediterranean Corridor [1] that stretches from Helsinki to La Valletta.

The current railway follows a route established in 1860, winding up the 1,371-metre-high mountain road with steep slopes of up to 26%. This design limits train speed and maximum load capacity, requiring at least two locomotives on the Italian side and three on the Austrian side. As a result, the existing railway is not competitive for cross-border freight or passenger transport.

The new Brenner Base Tunnel addresses these issues on the most critical part of the stretch by providing a nearly flat, straight route. At 64 km, it will be the world’s longest underground railway tunnel. With slopes of only 4 to 7 %, it runs 580 meters below the Brenner Pass.

The tunnel will reduce the Fortezza – Innsbruck line by 20 km. In the planning phase [2], freight trains were estimated to reach speeds of 160 km/h, and passenger trains up to 250 km/h, cutting travel time from 80 to just 25 minutes. The Brenner Base Tunnel [3] will consist of two single-track tunnels, each 8.1 m wide and spaced 40 to 70 metres apart.

Traffic through these tunnels will be one-way, and they will be connected with bypasses every 333 metres for safety. A smaller exploratory tunnel will run between and below the two main tunnels, used for drainage, maintenance, and technical installations. The excavations on the pilot tunnel have provided important knowledge on the rock mass, which reduced construction risk, costs, and times to a minimum.

To the south, the new line will connect to Fortezza via two single-track tunnels. To the north, it will link to the Innsbruck bypass and the lower Inn valley railway, as well as to Innsbruck railway station. The Brenner Base Tunnel is expected to move up to 50 million tonnes of freight annually, helping shift goods transport from road to rail, thereby reducing environmental impact in the sensitive Alpine region.

This is crucial given the effects of heavy road traffic on the area’s ecological system.

State of play

Out of seven construction works, four constructions sites are active: three in Austria and one in Italy. Key achievements include:

Completion of Lot H71 Isarco river underpass in December 2023, Lot H52 Hochstegen in December 2023, and Lot H33 Tulfes-Pfons in September 2021.
Lot H21 Sill Gorge: the works started in August 2020 and are scheduled to run to the end of 2024. Once completed, it will provide the link between the northern end of the Brenner Base Tunnel and the central station in Innsbruck.
Lot H41 Sill Gorge-Pfons: works are ongoing since January 2022.

In total, approx.

22.5 km of main tunnel tubes and 38 cross passages with a total length of approx.

2.3 km will be excavated within this construction lot. The two TBMs “Ida” and “Lilia” have already excavated more than half of the planned tunnel stretches.
Lot H53 Pfons-Brenner: the works started in May 2023. The two TBMs will drive a stretch of 7.6 km (a total of approx.

15.2 km) in each main tunnel tube.
Lot H61 Mules 2-3: the works started in 2011. The TBM “Virginia” reached the Austro-Italian state border in 2023, the TBM “Flavia” still needs to excavate 1.9 km of the western main tube to reach her destination. At the end of the construction period, expected in December 2024, 39.8 km of the main tubes and 14.8 km of the exploratory tunnel will be excavated, including the emergency stop in Trens and its access tunnel as well as the bypasses which connect the main tubes every 333 m.

A total of approximately 65 km of tunnels will be excavated. Once this construction lot is finished, all excavation activities in the Italian project area will be complete.
By December 2023, 75% of the Brenner Base Tunnel excavation was complete.

EU funding to BBT

The EU has financed the Brenner Base Tunnel from the early phases of feasibility and environmental studies under the TEN-T programme to further studies and construction works under the CEF Transport programme. The total EU contribution planned until end of 2025 amounts to EUR 2.3 billion.

In particular, under the TEN-T, the project received EUR 432,46 million for the Base Tunnel itself and for the southern and northern accesses. Under CEF 1, three grants were awarded for a total amount of EUR 1.2 billion. The main objectives were to carry out some preparatory studies as well as the excavation of the main tunnels and the correlated ancillary works.

Finally, under CEF 2 four grant agreements were signed: one grant of EUR 700 million to continue the excavation of remaining sections and the planning of the rail equipment; and three grants for a total amount of EUR 160 million to plan and work on the base tunnel accesses routes.

About CEF Transport

Since 2014, CEF Transport has supported over 1,500 projects [4] with a total amount of EUR37.5 billion. Under the 2021-2027 programming period, EUR25.8 billion has been made available for grants to co-fund Trans-European Transport Network [5] (TEN-T) projects in EU Member States.

References

^ Scandinavian-Mediterranean Corridor (transport.ec.europa.eu)
^ planning phase (ec.europa.eu)
^ Brenner Base Tunnel (ec.europa.eu)
^ over 1,500 projects (cinea.ec.europa.eu)
^ Trans-European Transport Network (cinea.ec.europa.eu)