The Brenner Base Tunnel (BBT) is a straight, flat railway tunnel between Austria and Italy. It runs from Innsbruck to Fortezza (55 km). If we add the Innsbruck railway bypass, which has already been built and which is the endpoint for the Brenner Base Tunnel, the entire tunnel system through the Alps is 64 km long. It is the longest underground rail link in the world.

Tunnels & tubes
Base tunnel
Exploratory tunnel
Logistics & drainage
Safety
Length
Geology
Tunnels & tubes
Tunnels & tubes

The BBT is a complex tunnel system. Besides the two main tubes and the exploratory tunnel, there are connecting tunnels, side tunnels and emergency stops plus four lateral access tunnels. A single track runs through each of the two main tubes.

Base tunnel
Base tunnel

We speak of a base tunnel when a tunnel runs through a mountain without noticeable sloping (so it may also be called a low-gradient railway). Base tunnels are built almost only through high mountain ranges.

Exploratory tunnel
Exploratory tunnel

The exploratory tunnel is important to obtain further information about the inside of the mountain and therefore plan the construction of the main tubes with a higher degree of precision.

Logistics & drainage
Logistics & drainage

During the construction of the main tubes, the spoil will be removed through the exploratory tunnel. Construction can therefore continue undisturbed. The exploratory tunnel also serves as a drainage tunnel for underground waters that collect in the entire tunnel system.

Safety
Safety

Both main tunnels are linked every 333 m by connecting side tunnels. These are safe areas in which passengers can find refuge and reach the other tunnel. From there, a rescue train can bring them to one of the three emergency stations. An access tunnel leads from these underground stations to the open air.

Length
Length

It stretches for 64 km between Fortezza and the tunnel entrance in Tulfes, near the Innsbruck bypass that was built in 1994. The length of the tunnel from Fortezza to Innsbruck is 55 km.

Geology
Geology

The geological information we have is based on preliminary prospection studies that have been going on for decades. So far 200 prospection borings have been carried out, in which over 35,000 m of stone were removed from the mountain, to evaluate the rock mass along the planned tunnel route.

The BBT consists of two tubes, each 8.1 m wide, running 70 m apart from one another. These tubes are each equipped with a single track, meaning that train traffic through the tubes is one-way. The two tubes are linked every 333 m by connecting side tunnels. These can be used in emergencies as escape routes. This configuration conforms to the highest security standards for tunnels.

A peculiar feature of the Brenner Base Tunnel (BBT) is the exploratory tunnel running from one end to the other. This tunnel lies between the two main tunnels and about 12 m below them and with a diameter of 5 m is noticeably smaller than the main tubes. The excavations currently underway on the exploratory tunnel should provide information on the rock mass and thereby reduce construction costs and times to a minimum. The exploratory tunnel will be essential for drainage when the BBT becomes operational.

The BBT runs for 64 km between Tulfes/Innsbruck and Fortezza, making it the longest underground railway stretch in the word. The BBT ends in Innsbruck in the existing railway bypass tunnel, which ends in Tulfes. A new rescue tunnel is being built running parallel to the bypass. The two-tube tunnel system between Innsbruck and Fortezza is 55 km long.

The slope in the base tunnel is 6.7 ‰ on the northern side and 4 ‰ on the southern flank of the Brenner. The apex height is 790 above sea level, lying 580 m below the Brenner Pass itself (1,371 m).

Basic data
TEN Corridor: SCAN-MED (Scandinavia - Mediterranean) 
Length of the new Brenner railway line from Munich to Verona425 km
Total tunnel length from the Innsbruck bypass to Fortezza64 km
Length of the base tunnel from the Innsbruck portal to the Fortezza portal55 km
Internal diameter of main tunnels8.1 m
Internal diameter of exploratory tunnelmin. 5 m
Longitudinal grade4.0 ‰ – 6.7 ‰
Design speed for goods trains120 km/h
Design speed for passenger trainsmax. 250 km/h
Energy supply for railway traction25 kV 50 Hz
Control and command systemETCS Level 2
Elevation at the upper surface of the rails at the Innsbruck portal608.8 m
Elevation at the upper surface of the rails at the highest point794 m
Elevation at the upper surface of the rails at the Fortezza portal747.2 m
Expected costs (price basis: 01.01.2017)7,765 Mio. €
Expected costs including risks that are presumed to occur but are not quantifiable (price basis: 01.01.2017)8,282 Mio. €
Expected costs including future adjustments for Inflation (CIPE resolution pending)8,384 Mio. €
Planning and construction phases:
Phase I: preliminary project and prospection
Phase II: final project and Environmental Impact Assessment
Phase IIa: exploratory section
Phase III: main tunnel
1999–2003
2003–2010
2007–2013
2011–2026
4 access tunnels
The lateral access tunnels in Ampass, Ahrental, Wolf bei Steinach a.B. and in Mules link the Brenner Base Tunnel with the outside world.
333 meters
Smaller cross-tunnels connecting the two main tubes are located every 333 m.
3 Emergency Stopping Areas
In case of unforeseen events, trains can halt at the underground emergency stops (Innsbruck, St. Jodok, Trens).
35.000 meters
For the project planning, 35,000 metres of prospection boreholes were drilled. These provide information on the geological conditions inside the mountain.
25 kV 50 Hz
Railway traction will be 25 kV 50 Hz. The European-level signalling system ERMTS II will be installed.