A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube construction techniques rather than traditional tunnel boring methods.
The Bern-Lötschberg-Simplon-Bahn (BLS), known between 1997 and 2006 as the BLS Lötschbergbahn, was a Swiss railway company. In 2006 the company merged with Regionalverkehr Mittelland AG to form a new company called BLS AG.
The Gotthard Base Tunnel 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 57.09 km (35.5 mi), it is the world's longest railway and deepest traffic tunnel and the first flat, low-level route through the Alps. It lies at the heart of the Gotthard axis and constitutes the third tunnel connecting the cantons of Uri and Ticino, after the Gotthard Tunnel and the Gotthard Road Tunnel.
The Gotthard Road Tunnel in Switzerland runs from Göschenen in the canton of Uri at its northern portal, to Airolo in Ticino to the south, and is 16.9 kilometres (10.5 mi) in length below the St Gotthard Pass, a major pass of the Alps. At time of construction, in 1980, it was the longest road tunnel in the world; it is currently the fifth-longest. Although it is a motorway tunnel, part of the A2 from Basel to Chiasso, it consists of only one bidirectional tube with two lanes. With a maximum elevation of 1,175 metres (3,855 ft) at the tunnel's highest point, the A2 motorway has the lowest maximum elevation of any direct north-south road through the Alps.
A horseshoe curve is a class of climbing curve in a roadbed that reverses turn direction (inflection) twice on either side of a single tight curve that varies through an angle of about 180 degrees or more.
Semmering is a mountain pass in the Eastern Northern Limestone Alps connecting Lower Austria and Styria, between which it forms a natural border.
The Simplon Tunnel is a railway tunnel on the Simplon railway that connects Brig, Switzerland and Domodossola, Italy, through the Alps, providing a shortcut under the Simplon Pass route. It is straight except for short curves at either end. It consists of two single-track tunnels built nearly 15 years apart. The first to be opened is 19,803 m (64,970 ft) long; the second is 19,824 m (65,039 ft) long, making it the longest railway tunnel in the world for most of the twentieth century, from 1906 until 1982, when the Daishimizu Tunnel opened.
The Brenner Base Tunnel is a 55-kilometre-long (34 mi) railway tunnel under construction through the base of the Eastern Alps beneath the Brenner Pass. Upon completion, it will be the second or third longest railway tunnel in the world, after the Gotthard Base Tunnel in Switzerland and the Mont d'Ambin Base Tunnel between France and Italy. It will run from near Innsbruck, in Austria, to Franzensfeste, in Italy, replacing part of the current Brenner railway. The line is part of Line 1, the Berlin to Palermo route, of Trans-European Transport Networks (TEN-T).
High-speed rail in Italy consists of two lines connecting most of the country's major cities. The first line connects Turin to Salerno via Milan, Bologna, Florence, Rome and Naples, the second runs from Turin to Venice via Milan and Verona, and is under construction in parts. Trains are operated with a top speed of 300 km/h (190 mph).
The Engerth locomotive was a type of early articulated steam locomotive designed by Wilhelm Freiherr von Engerth for use on the Semmering Railway in Austria. The distinctive feature of the Engerth design was an articulated tender as part of the main locomotive frame. Some of the weight of the tender therefore rested on the driving wheels, improving adhesion, while articulation allowed the locomotive to navigate the narrow curves of mountain railways.
The Lötschberg line is a railway in Switzerland, connecting Spiez in the canton of Bern with Brig in the canton of Valais. It crosses the Bernese Alps, from the Bernese Oberland to Upper Valais, through the Lötschberg Tunnel in the middle of the line. Together with the Simplon Tunnel south of Brig, it constitutes one of the major railways through the Alps and an important north-south axis in Europe. The Lötschberg axis is backed by the lower and longer Lötschberg Base Tunnel, part of the New Railway Links through the Alps project.
The Südostbahn – commonly abbreviated to SOB – is a Swiss railway company, and a 1,435 mmstandard gauge network in Central and Eastern Switzerland. It resulted from the merger of the original SOB with the Bodensee–Toggenburg railway (BT) at the end of 2001.
The Albula railway line is a single track metre gauge railway line forming part of the core network of the Rhaetian Railway (RhB), in the canton of Graubünden, Switzerland. It links Thusis on the Hinterrhein at 697 m (2,287 ft) and Filisur at 1,080 m (3,540 ft) with the spa resort of St. Moritz in Engadine at 1,774 m (5,820 ft).
The Pistoia–Bologna railway is an Italian railway connecting Bologna to Pistoia and was the first line through the Apennines between Tuscany and Emilia-Romagna. It is also known in Italian as the Ferrovia Porrettana or the Transappenninica ("trans-Apennines"). It was officially called the Strada ferrata dell'Italia Centrale and was officially inaugurated by King Victor Emmanuel II in 1864.
The Eurasia Tunnel is a road tunnel in Istanbul, Turkey, crossing underneath the Bosphorus strait. The tunnel was officially opened on 20 December 2016 and opened to traffic on 22 December 2016.
The Turin–Lyon high-speed railway is an international rail line under construction between the cities of Turin and Lyon. It is intended to link the Italian and French high-speed rail networks and will be 270 km (170 mi) long. The core of the project is its international section, which will cross the Alps through the Mont d'Ambin Base Tunnel between the Susa Valley in Piedmont and Maurienne in Savoie. At 57.5 kilometres (35.7 mi), that tunnel will be the longest rail tunnel in the world, ahead of the 57.1 km (35.5 mi) Gotthard Base Tunnel. The estimated total cost of the line is €25 billion, of which €8 billion is for the international section. The latter is the only part of the line where construction has started.
The Ayaş Tunnel is a railway tunnel under construction near Ayaş town of Ankara Province in Central Anatolia, Turkey. It was initially projected to shorten the railway line connecting Ankara with Istanbul.
High-speed rail in Switzerland consists of two new lines and three new base tunnels, including the world's longest railway and deepest traffic tunnel: the Gotthard Base Tunnel whose length is 57 km (35 mi). Each of these tunnels have a technical maximum speed of 250 km/h (155 mph), which is reduced, at least in the Gotthard Base Tunnel and the Ceneri Base Tunnel, to a maximum authorized speed of 230 km/h (145 mph), for environmental and economic reasons.
The West railway between the capital Vienna and Salzburg is being upgraded. Most new sections have a continuous maximum design speed of 250 km/h (155 mph).
The Semmering Base Tunnel is a railway tunnel under construction between Gloggnitz and Mürzzuschlag in Austria underneath the Semmering Pass. The existing route is 41 km in length and the Semmering Base Tunnel will be 27.3 km in length. The new route will offer time savings of up to 30 minutes, partly on account of the shorter route and partly on account of the higher speed limit.
![Schematic representation of a normal base tunnel construction method in Europe; they have two tubes connected every few hundred meters in order to enable evacuation in case of emergency
[image shows an evacuation station of the base tunnel Gotthard, the longest railway tunnel in the world - 57 km (35 mi)] GBT-ESS.png](http://upload.wikimedia.org/wikipedia/commons/thumb/4/48/GBT-ESS.png/330px-GBT-ESS.png)