The construction team with helmets and working clothes in the tunnel from left to right: Adrian Fontana, ÖBA Manager; Andrea Lussu, BBT Project Manager for the Tulfes-Pfons construction lot; Christian Kaiser, Technical Management ARGE Tulfes-Pfons; Konrad Bergmeister, BBT SE Management Board; Sebastian Grüllich, STRABAG Construction Manager tunnel boring machine.

VirtuRail: With an Autonomous Train into the Heart of the Tunnel

Efficient supply transports thanks to the latest technology: during the construction of the Brenner Base Tunnel trackless, autonomous trains were used for the first time. We took a look inside the mountain.

It’s a warm day in June 2018 in the Tyrolean Alps. But there is little evidence of this in the exploratory tunnel for the Brenner Base Tunnel. The shotcrete walls, illuminated by lamps, emit a pleasant coolness. The moisture of the mountain collects on the concrete floor. Two cones of light appear in the dark: “Christl“, a train pulling five wagons, passes by at about 20 km/h. Its destination is the tunnel boring machine (TBM), which it supplies with prefabricated concrete segments – so-called “Tübbings“. Thanks to the autonomous VirtuRail® system, Christl doesn’t need any rail tracks. This makes it a world-first, which adds another innovation to tunnelling at STRABAG.

the new multiservice vehicle at the tunnel exit
Christl on fire: the new multiservice vehicle at the tunnel exit. © ARGE Tulfes Pfons/STRABAG AG

Self-driving train on rubber tyres

Today, Business Unit Manager Christian Kaiser and TBM Site Manager Sebastian Grüllich look back with satisfaction on their work with Christl. Together with their team, they have implemented the drive for the 15 km long exploratory tunnel as well as the other 30 km long tunnels for the Tulfes-Pfons tunnel section. The Multi Service Vehicle (MSV) developed by the STRABAG experts together with partner companies played an important role in this.

“This is the first time that we used the approximately 55 m long, autonomous trains to provide uninterrupted supplies to the tunnel boring machine,“ says Sebastian Grüllich. The vehicles supplied by logistics system specialist ROWA are rubber-tired – a practical approach that eliminates the need for track installation and operation.

What do you think? How many kilometres of supply runs did the self-driving trains complete at the Tulfes-Pfons construction site by the end of the project?
50 km
4,000 km
10,000 km
250,000 km
The correct answer is
250,000 km
Sorry, that’s not right.
The correct answer is
250,000 km

Smart train system ensures new records

The five coupled wagons can transport 95 tons of material from the tunnel portal to the TBM without reloading. For comparison: standard MSVs achieve a maximum payload of 55 tons. “The trains contributed greatly to the world tunnel propulsion record of 61.04 m in 24 hours,“ says Grüllich proudly. Another special achievement is its ability to overcome a 12 % slope over a distance of more than 2 km.

This was also a major goal behind the train’s development: the gradient made track-bound supply impossible. “The MSVs available on the market so far were out of the question due to their poor track keeping behaviour and their small size.

In all its glory: The tunnel boring machine with the official identification “Hard Rock Gripper BM S-932“ is around 200 m long and weighs 1,800 t. © ARGE Tulfes-Pfons/STRABAG AG
Perfect teamwork (from left to right): Adrian Fontana, Head of Construction Supervision; Andrea Lussu, BBT Project Manager ARGE Tulfes-Pfons; Christian Kaiser, technical Managing Director ARGE Tulfes-Pfons; Konrad Bergmeister, CEO of BBT SE; Sebastian Grüllich, STRABAG TBM Site Manager. © ARGE Tulfes-Pfons/STRABAG AG
Great cheer for the team in the Brenner Base Tunnel: The TBM reached the 15,000-metre mark in the exploratory tunnel in July 2019. © ARGE Tulfes-Pfons/STRABAG AG
A hard job: the TBM has to eat its way through phyllite and slate. © ARGE Tulfes-Pfons/STRABAG AG

Safe through the mountain on a virtual track

A look back to June 2018: The starting station for Christl is at the tunnel portal. Here the team takes over the loading. Shotcrete, rock anchors, reinforcing mats, precast concrete segments – the train can carry them all. Then Christl begins its approximately one-hour trip to the tunnel boring machine. A steering wheel can`t be found in the driver’s cab. The VirtuRail® system from MobileTronics steers all 18 axles electronically so that they precisely follow a virtual track.

An additional driver assistance system automatically controls the first axle in the tunnel. And thanks to state-of-the-art navigation sensors, it is also capable of recognising possible obstacles. In this way, the train safely navigates the 90-degree bend at the end of the access tunnel.

55 m
95 tons
Transport capacity
500 hp
25 km/h
Maximum speed in operation

Joystick instead of steering wheel in the operator cabin

In automatic mode, the driver merely controls the speed and uses a joystick to inform the system in which section of the tunnel the MSV is currently located.

“By the end of the project, 250,000 km of supply trips were successfully completed without a single accident,“ says Christian Kaiser. Given the difficult conditions involved in underground transport, such as dust and moisture accumulation as well as mechanical strain on the equipment, that’s a noteworthy achievement.

“The use of a total of six MSVs also reduced the fuel consumption and exhaust emissions in the tunnel compared to other known supply concepts such as trucks,“ summarises the Business Unit Manager. Besides the long trains Annemarie, Christl and Emma there were also the short trains Bärbel (self-rescue), Dorli (special transports) and Florian (external rescue fire brigade train) in operation.

World’s first autonomous supply run

Can the autonomous vehicle operate completely without a driver? The proof was provided by an impressive demonstration in December 2018. For the first fully autonomous supply run, the train technology was complemented with electronic “traffic signs“ in the Brenner Base Tunnel. The MSV read its location from these signs and then defined the parameters for the next leg of the trip.

“I was surprised at how smoothly the driverless train moves. The MSV also interacted perfectly with the other vehicles operating in the tunnel,“ Grüllich recalls. The experiment was a complete success and demonstrated the potential of autonomous operation. However, in the construction of the exploratory tunnel for the Brenner Base Tunnel, it didn’t go beyond this one demonstration. “Since the end of the drive at 15 km came in sight so quickly, the move to autonomous driving in full operation would not have paid off in time,“ Grüllich explains.

Electric power as the next step

Nevertheless, this result plays a pioneering role for the future. “In the future, all material logistics could be carried out remotely via a central control station,“ says Christian Kaiser. “That would be a huge opportunity, especially on larger construction sites with several tunnel boring machines.“ The expert sees the next step in the development of Multi Service Vehicles in the conversion to an electric or hybrid driving system.

STRABAG and the Brenner Base Tunnel

The 45 km long Tulfes-Pfons section is a part of the construction project for the Brenner Base Tunnel (BBT), the longest underground railway in the world. Located at the northeast end of the tunnel, the section extends from the town of Tulfes to Pfons at the Brenner. In addition to the main tunnel and the connecting tunnel, the consortium of STRABAG and Salini-Impregilo is also building additional structures such as an exploratory tunnel and an emergency stop. The contract value for this project was around € 380 million.

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Christl has now reached the trailer ofthe tunnel boring machine. Here the vehicle has to enter exactly in the middle. Within 30 minutes, the team then unloads the heavy tunnel segments, using cranes. The empty shotcrete buckets are moved back into the wagons. Christl returns to the site mobilisation area. The next round can start – and soon, the next tunnel project.

Design & Engineering
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