57 kilometers of Swiss precision engineering

The Gotthard Base Tunnel is the jewel in the crown of the new Alp Transit rail network, providing links through the Alps, across Switzerland, and beyond. This architectural wonder is not only the world’s longest rail tunnel – it also showcases the finest Swiss precision engineering. The project was completed in extraordinary settings, which demanded the utmost precision and ingeniously adapted technology.

Covering a distance of 57 kilometers, the Gotthard Base Tunnel stretches from its north portal at Erstfeld in the Swiss Canton of Uri, to its south portal at Bodio in the Canton of Ticino. To create the two single-track main tunnels and the safety, ventilation and cross tunnels, 28.2 million tons of rock had to be excavated since the first blast 17 years ago. A truly remarkable feat of Swiss engineering.


A quick look at the figures shows just how different the new construction is to the existing Gotthard Tunnel. Taking a train today bound for the southern Alps, you notice how the train makes a tortuous climb on a winding track through helical tunnels to cross the mountains at an elevation of 900 meters above sea level. There are “only” 1,100 meters of mountain above you – a relatively modest weight compared to the new Base Tunnel. The new tunnel’s maximum elevation is 550 meters above sea level, and the route makes only minor climbs with no tight curves. However, that leaves a massive 2,300 meters of rock above your head. Which takes some getting used to... But it is well worth it as the trip from Zurich to Lugano will now take only two hours (45 minutes less than before), and Milan will be just three hours away. These impressive figures have been received with a great deal of enthusiasm – not only from the Swiss public, which already loves rail travel, but also from the technicians.

Safely darting through the tunnel at 250 km/h

It goes without saying that safety is paramount in a tunnel where in the near future more than 200 trains a day will dart along the rails at speeds of up to 250 km/h. The two main tunnels are connected every 325 meters by crosscuts that allow train passengers to escape to the other tunnel in case of a fire. Yet fire is not the biggest danger; suffocation is an even greater concern. Each tunnel tube has two emergency-stop stations 600 meters in length that allow evacuation of up to 1,000 passengers. But to make sure it never comes to this, the tunnel is equipped with a myriad of sensors, monitoring devices and controllers, which are connected to the control centers at the north and south portals via thousands of kilometers of optical fiber cables.

Caged fire detectors

Fire detection in the four emergency-stop stations is ensured by three different detection systems, which control the air dampers directly should passengers need to be evacuated. The controllers check and record the monitoring data every few milliseconds. A distinctive feature of the system is the FibroLaser fire detection technology from Siemens. Typically, FibroLaser cables are mounted at a distance of 5 cm from the wall because this allows optimal transmission of temperature readings. For technical reasons, however, in the Gotthard Base Tunnel they were mounted directly against the concrete wall. In addition, FibroLaser sensors on the floor watch for initial signs of danger. For example, a stuck wheel on a train or leaking fluid can catch fire. For the FibroLaser floor installations, armored cables were used to guarantee protection against water spray and mechanical stress. For ceiling installations, cables without metal were used to avoid interferences with the overhead lines.


In addition to FibroLaser, the tunnel is equipped with thermal imaging cameras and smoke detectors that continuously measure the temperature and check the air for smoke particles. To protect them against the harsh environment in the tunnel, these were enclosed in cages in another custom design for the GBT. Everything is built for trains capable of speeds up to 270 km/h, with a little room for maneuver if needs be.

Redundant systems

Once trains are operating along the Gotthard line, the tunnel must of course be vacated. To prevent accidents during maintenance, for example, the doors in the crosscuts are monitored. The 40-meter tubes are installed with hundreds of distributed Simatic controllers and interface modules. Comprising as many as 60,000 data points, these Siemens systems monitor the doors and communicate with numerous electric components. The data is transmitted via Ethernet by Scalance routers, each tunnel tube having seven group computers. These, in turn, are connected to the master computers. The WinCC OA process visualization system from Siemens has been installed on both the group and master computers. All the data gathered is then transmitted to the higher-level tunnel management system. Redundant tunnel and train control systems from Siemens form the backbone of the two tunnel control centers at the north and south portals. These systems monitor and control all elements of the tunnel infrastructure and rail technology.

Cutting-edge rail technology

As part of the Transtec Gotthard AG consortium, Alcatel-Lucent Schweiz AG and Thales Rail Signalling Solutions commissioned Siemens to supply the technology for monitoring the trains with railway control systems (Iltis and TAG/Tunnel Automation Gotthard – Thales Rail Signalling Solutions), and for displaying and operating all other tunnel control technology installations (Alcatel-Lucent Schweiz AG). Simply put: all the technical installations that will ensure smooth rail traffic.

Eray Müller

Picture credits: AlpTransit Gotthard / Hans Stuhrmann


On May 31st, 1879, Werner Siemens ushered in a new era of rail transport with three small cars drawn by an electric locomotive at the Berlin Industrial Exhibition.


Only two years later, Gotthard Railway was already keen to electrify its 15-kilometer tunnel between Göschenen and Airolo. Yet the initial plans to construct Switzerland’s very first electric railway section were never realized. According to calculations at the time, an express train traveling at 45 km/h and weighing around 160 tons would have required an electric engine with the equivalent power of at least 400 horses. The same power would be needed for a freight train traveling at 25 km/h and weighing 400 tons.


Experts at Siemens & Halske believed that electric drive could indeed be used in the tunnel, but instead suggested using four-wheel locomotives with 100 to 120 HP, which could be coupled together until there was enough power to drive the train.


Yet this solution was never put to the test, and the Gotthard Tunnel did not see its first electric locomotive until four decades later on July 1st, 1920. Instead, a mail train with two small steam engines began service on January 1st, 1882.

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