The Gotthard Base Tunnel (GBT; , , ) is a railway tunnel through the Alps in Switzerland. It opened in June 2016 and full service began the following December. With a route length of , it is the world's longest railway and deepest traffic tunnelThe world longest tunnel for transport of people is the Guangzhou Metro Line 3 in China (60 km). Reference: Nic Ulmi, "Des trous suisses remplis d'imaginaire" [interview with André Ourednik], Horizons, magazine of the Swiss National Science Foundation and the Swiss Academies of Arts and Sciences, number 118, September 2018, pages 22-23. and the first flat, low-level route through the Alps.Yücel Erdem, Tülin Solak, Underground Space Use. Analysis of the Past and Lessons for the Future, CRC Press, 2005 (p. 485) Located at the heart of the Gotthard axis, it is the third tunnel to connect the cantons of Uri and Ticino, after the Gotthard Tunnel and the Gotthard Road Tunnel.
The GBT consists of a large complex with, at its core, two single-track tunnels connecting Erstfeld (Uri) with Giornico (Ticino) and passing below Sedrun (Grisons). It is part of the New Railway Link through the Alps (NRLA) project, which also includes the Ceneri Base Tunnel further south (opened on 3 September 2020) and the Lötschberg Base Tunnel on the other main north–south axis. It is referred to as a "base tunnel" since it bypasses most of the existing vertex line, the Gotthard railway line, a winding mountain route opened in 1882 across the Saint-Gotthard Massif, which was operating at its capacity before the opening of the GBT. The new base tunnel establishes a direct route usable by high-speed rail and heavy freight trains.
The main purpose of the Gotthard Base Tunnel is to increase local transport capacity through the Alpine barrier, especially for freight on the Rotterdam–Basel–Genoa corridor. The tunnel is specifically meant to shift freight to trains from trucks, and thereby to reduce environmental damage and deadly road crashes. The tunnel also provides a faster connection between the canton of Ticino and the rest of Switzerland, as well as between northern and southern Europe, cutting the Basel/Zürich–Lugano–Milan journey time for passenger trains by one hour (and from Lucerne to Bellinzona by 45 minutes).
After 64 percent of Swiss voters accepted the NRLA project in a 1992 referendum, the first preparatory and exploratory work began in 1996. Construction began in November 1999 at Amsteg. Drilling operations were completed in March 2011. Completed in 2016, the final cost was reported to be CHF 12.2 billion ( billion). A freight train derailment in August 2023 forced the tunnel's closure for over a year before reopening in September 2024.
Description The Gotthard Base Tunnel, with a length of and a total of of tunnels, shafts and passages, is the longest railway tunnel in the world,Excluding subway tunnels that lie near the surface. See also: List of longest subway tunnel sections and List of longest tunnels. with a geodetic distance of between the two portals. It is also the first flat route through the Alps or any other major mountain range, with a maximum elevation of above sea level, corresponding to that of Bern. It is the deepest railway tunnel in the world, with a maximum depth of , comparable to that of the deepest mines on Earth. Without ventilation, the temperature inside the mountain reaches .
Like the two other tunnels passing below the Gotthard, the Gotthard Base Tunnel connects two Alpine valleys across the Saint-Gotthard Massif: the Urner Reusstal in the canton of Uri, in which flows the river Reuss, and the Valle Leventina, the largest valley in the canton of Ticino, in which the river Ticino flows. Unlike most other tunnels, the Gotthard Base Tunnel passes under several distinct mountain massifs, two of them being major subranges of the Alps, the Glarus Alps and the Saint-Gotthard Massif, with the valley of the Anterior Rhine, the Surselva in the canton of Graubünden, between them. The tunnel passes under these two ranges more than below the Chrüzlistock () and the Piz Vatgira (, near the Lukmanier Pass). While the cantons of Uri and Ticino are part of the German- and Italian-speaking areas of Switzerland respectively, the Surselva is mainly Romansh-speaking.
The Alps strongly influence the European climate – and that of Switzerland in particular – and there can be substantially different weather conditions at each end of the GBT, described by the Ticinese architect Mario Botta: "The light changes at the Gotthard: that of the Mediterranean Sea is not the same as that of the continent, that of the central lands, that of Europe far away from the sea." On average, the temperature is about higher on the south side than the north side, but on some days, temperature differences are well over .See the climate tables of Altdorf and Grono, two towns situated near each end of the tunnel. See also normals/climate-diagrams-and- normal-values-per-station.html?region=Map Climate diagrams and normal values per station (MeteoSwiss).
The north portal lies in the north of the municipality of Erstfeld at an elevation of , east of the Reuss. There, the tunnel penetrates the western slopes of the Bälmeten and Chli Windgällen (although only marginally) before passing below the valley of the Chärstelenbach, a creek in the Maderanertal. From there, the tunnel runs parallel to the small valley of Etzli, below the Witenalpstock. The main crest of the Glarus Alps, which is the watershed between the Reuss and the Anterior Rhine, is crossed below the Chrüzlistock, the crest having an elevation of about at this point. From the crest and border, the tunnel runs parallel to the small valley of the river Strem (Val Strem) before passing below Sedrun and the Anterior Rhine. From the bottom of the valley, the tunnel proceeds towards the valley of the Rein da Nalps (Val Nalps) and passes east of Lai da Nalps, before crossing the Gannaretsch range below the western summit of Piz Vatgira (). This is the deepest point of the tunnel, with a rock layer of above it. The tunnel then passes below the valley of the Rein da Medel (Val Medel) and west of Lai da Sontga Maria. After a few kilometres the tunnel crosses the watershed between the Anterior Rhine and the Ticino, just north of Pizzo dell'Uomo (). This point corresponds to the main chain of the Alps, and is the main drainage divide between the Rhine and the Po. For a few kilometres, the tunnel passes below two western tributaries of the Brenno in the Valle Santa Maria before crossing the last range, west of the Passo Predèlp (about ) and east of Faido. It then follows the eastern slopes of the large Valle Leventina, the valley of the Ticino, for about to the south portal at Giornico, at an elevation of , just before Biasca, where the Brenno converges with the Ticino.See Swisstopo topographic maps with catchment areas layer: map.geo.admin.ch.
The closest railway stations to the portals are Altdorf and Biasca. The first regularly served railway stations on the base line (as of 2016/17) are those of Arth-Goldau (Schwyz), a railway node with links to Lucerne and Zürich, and Bellinzona (the "Gate of Ticino"), with links to Locarno, Luino and Lugano (via the Monte Ceneri Rail Tunnel). The journey from Arth-Goldau to Bellinzona takes not more than an hour. The station of Altdorf is planned to be served by 2021. There also have been talks of using that of Biasca. The travel between Altdorf and Biasca would last less than 25 minutes.
History Background
Since the 13th century, the Gotthard Pass has been an important trade route from northern to southern Europe. Control of its access routes led to the birth of the Swiss Confederacy. The Gotthard Pass is located halfway between Lake Lucerne and Lake Maggiore. It is the shortest link between the navigable Rhine and the Po. Before modern transport, the traverse of the pass took days, and snow makes it a challenge in winter.
Quite late, compared to other current top-importance routes through the Alps (e.g. Simplon, San Bernardino, Brenner, Mont Cenis), namely in 1830, the first Saint-Gotthard Pass road was established after centuries-long usage of a bridle path. From 1842 onwards, a daily course by the Gotthard Post, a stagecoach drawn by five horses with ten seats, still took about 23 hours from Como to Flüelen. It would last until 1921.
In 1882, with the inauguration of the Gotthard Railway Tunnel, the travel time between Altdorf and Biasca was reduced dramatically to only hours, though often accompanied with overnight stays in large Fin de siècle-hotels, for example in Biasca. In those days, it was still an adventure and it was only affordable to the rich. Electrification of the railway line in 1922 significantly reduced travel time again. Refilling water boilers of steam locomotives was no longer necessary. There were also the technical advantages of electrical engines and future technical improvements.
From 1924, car transport on trains through the railway tunnel began. The road between Göschenen and Airolo over the summit of the pass, comporting notably the Schöllenen ravine and the Tremola, had countless hairpin turns and serpentine curves, dropping in altitude. It posed a huge challenge for automobiles of those days. From 1953 onwards, the pass road was sequentially improved and expanded at several sections along the Gotthard route, finally ending in 1977 with the opening of an expressway fully circumventing the Tremola. In winter, however, due to the snow, cars could only cross the Gotthard on the train.
Transit time was further dramatically reduced with the opening of the Gotthard Road Tunnel and the finalization of the northern part of A2 motorway through the Urner Reusstal (in close proximity to the railway), with many additional tunnels (then leading from Basel to the Gotthard Road Tunnel), in 1980. With the completion in 1986 of the A2 motorway in the Valle Leventina, the main valley leading from Airolo down to Bellinzona, and the surmounting of the Monte Ceneri between Bellinzona and Lugano in 1983, finally a continuous motorway was established from the northern border of Switzerland in Basel to the southern border in Chiasso, or the shortest motorway route from North-German Hamburg as far as South-Italian Sicily, bringing down the competitiveness of the railway line. Passenger speed was also increased on the railway line with the use of tilting trains, notably the ICN, although maximum speed remaining far lower than on a modern straight high-speed line. Both modern motorway and historic railway rely on heavy rockfall and avalanche protection equipments and are exposed to harsh weather condition in winter.
After the opening of the auto tunnel, in 1980, traffic increased more than tenfold. The existing tunnel was at its capacity by 2013. A second tunnel will be built next to the first, following a national referendum. Construction started in 2021 and is scheduled to finish in 2027.
As early as 1947, engineer Eduard Gruner imagined a two-story base tunnel from Amsteg to Biasca, both rail and road, with a stop at Sedrun, to provide a faster and flatter passage through the Swiss Alps. Similarly to Gruner's idea, the GBT cuts through the Gotthard Massif some below the older tunnel. On the historic track only the Gotthard Railway trains up to when using two locomotives or up to with an additional bank engine at the end of the train are able to pass through the narrow mountain valleys and through spiral tunnels climbing up to the portals of the old tunnel at a height of above sea level. Since the GBT is in full service, standard freight trains of up to are able to pass this natural barrier.