Brenner Base Tunnel

A new era of rail connectivity across the Alps

The Brenner Base Tunnel (BBT) links Austria and Italy. The railway tunnel forms the centrepiece of the Scandinavian-Mediterranean TEN corridors stretching from Helsinki to Valletta and runs for 55 kilometres from Innsbruck to Franzensfeste. Taking into account the existing Inntal bypass tunnel, this results in the world’s longest underground rail link, with a total length of 64 kilometres. 

The BBT consists of two single-track main tunnel tubes, each 8,1 metres wide and spaced 40 to 70 metres apart. The two main tunnel tubes are connected every 333 metres by cross-passages, which serve as escape routes in the event of an incident. In addition, there are three emergency stopping points along the route where trains can come to a safe halt in the event of unexpected incidents.

A distinctive feature of the Brenner Base Tunnel is the continuous exploration tunnel running beneath the two single-track main tunnel tubes. It is situated centrally beneath the tubes at a depth of around 12 metres and has a diameter of 5 to 6 metres. In total, the Brenner Base Tunnel system comprises approximately 230 kilometres of tunnels. 

The almost horizontal tunnel alignment avoids the gradients of the existing Brenner line, which is more than 140 years old. The total cost of the project, which is scheduled for completion in 2032, is estimated at 10,5 billion euros.

STRABAG has been involved in the Austrian section of the BBT since 2009 and is contributing its expertise as a technical leader and problem-solver in geologically challenging conditions across various construction lots (EBN, AFA, KSP and ATP). At the heart of the BBT are the intersecting connecting tunnels, with a total length of around 7 kilometres, which link the east-west route of the Inn Valley Tunnel – completed in 1994 – with the north-south tubes of the BBT. This connection could only be achieved through the integration of the EBN, AFA and ATP construction lots by STRABAG. With the breakthrough in the exploratory tunnel in July 2020, Innsbruck was connected to construction lot H51, and with the geologically challenging auxiliary tunnelling ‘Iris’ in the summer of 2021, a further key foundation stone was laid for the main tunnel drives in construction lots H41/H53.

Scope of Work

• Construction of railway tunnel sections
• Tunnelling and underground construction works 
• Excavation of tunnel connections and link structures 
• Construction under complex geological conditions 
• Integration of multiple construction lots 
• Delivery of key infrastructure for the Brenner Base Tunnel