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Simplon tunnel from the Italian side

The Simplon Tunnel is an Alpine railway tunnel that connects the Swiss town of Brig with Domodossola in Italy, though its relatively straight trajectory does not run under Simplon Pass itself. It actually consists of two single-track tunnels built nearly 20 years apart. It was the longest railway tunnel in the world until the opening of the Seikan Tunnel in 1988 (see World's longest tunnels).

Work on the first tube of the Simplon tunnel commenced in 1898. The Italian king Victor Emmanuel III of Italy and the president of the Swiss National Council Ludwig Forrer opened the tunnel at Brig on 10 May 1906. The builders of the tunnel were Hermann Häustler and Hugo von Kager and the tunnel is 19,700 meters (64,633 ft) long. Work on the second tube of the tunnel started in 1912 and it was opened in 1921; it is 19,824 meters (65,039 ft) long.

Straight track Straight track
To Zermatt/Lausanne/Geneva
Straight track Junction from left
To Berne via Lötschberg Base Tunnel
Straight track Junction from left
To Berne via Lötschberg Tunnel
Station on track Station on track
Brig (MGB/SBB)
Track turning left Unknown route-map component "KRZo"
To Dissentis
Enter tunnel
Simplon Tunnel (19,803 m)
Unknown route-map component "tGRENZE"
ItalianSwiss border
Exit tunnel
Enter and exit short tunnel
Iselle tunnel (628 m)
Stop on track
Iselle di Trasquera
Enter tunnel
Trasquera tunnel (1,712 m)
Unknown route-map component "tSTRrg" Unknown route-map component "tKRZt" Unknown route-map component "tSTRlg"
Exit tunnel Exit tunnel Exit tunnel
Varzo spiral tunnel (2,966 m)
Stop on track Track turning left Track turning right
Enter and exit short tunnel
Varzo tunnel (81 m)
Enter and exit short tunnel
Mognatta tunnel (422 m)
Enter and exit short tunnel
Gabbio Mollo tunnel (568 m)
Enter and exit short tunnel
San Giovanni tunnel (425 m)
Enter and exit short tunnel
Rio Confinale tunnel (51 m)
Enter and exit tunnel
Rio Rido–Preglia tunnel (2,266 m)
Stop on track
Station on track Unknown route-map component "tKBHFl"
Domodossola / To Locarno
Junction to right
To Novara
Straight track
To Milan



Shortly after the opening of the first railway in Switzerland, each region began to favour a separate north-south link through the Alps towards Italy. Eastern Switzerland supported a line through the Splügen or the Lukmanier Pass, Central Switzerland and Zurich favored the Gotthard Pass and Western Switzerland supported the Simplon route.

In 1871 the first line was completed through the Alps, connecting Italy and France with the Fréjus Rail Tunnel.

On 1 July 1878 the railway company, Simplon Railway Company (French: Compagnie du chemin de fer du Simplon, S) was created to promote the project; it merged in 1881 with the company Western Swiss Railways (French: Chemins de Fer de la Suisse Occidentale, SO) to create the Western Switzerland–Simplon Company (French: Compagnie de la Suisse Occidentale et du Simplon, SOS). The French financiers of the SOS were able to secure finance for the tunnel in 1886. The company considered 31 proposals and selected one that involved the construction of a tunnel from Glis to Gondo, which would have been fully in Switzerland. From Gondo it would have continued on a ramp through the Divedro valley down to Domodossola.

At a Swiss-Italian conference held in July 1889 it was agreed, however, to build a nearly 20 kilometer-long base tunnel through the territory of both states. In order to secure credit for the tunnel, the SOS joined with the Jura–Bern–Luzern Railway to create the Jura–Simplon Railway (French: Compagnie du Jura–Simplon, SOS).

The participation of the Swiss government led to the signing of a treaty with Italy on 25 November 1895 concerning the construction and operation of a railway through the Simplon from Brig to Domodossola by the Jura–Simplon Railway. The route of the tunnel was determined by military considerations so that the state border between the two countries was in the middle of the tunnel, allowing either country to block the tunnel in the event of war.

On 1 May 1903, the Jura-Simplon Railway was nationalized and integrated into the network of the Swiss Federal Railways (SBB), which completed construction of the tunnel.



The construction of the tunnel was carried out by the Hamburg engineering company Brandt & Brandau of Karl Brandau and Alfred Brandt. On average 3000 people a day worked on the site. They were mostly Italians, who suffered under very poor working conditions. 67 workers were killed in accidents, many died later of diseases. During the work there were strikes, which led to the intervention of vigilantes and the Swiss army.

With up to 2,135 m of rock over the tunnel, temperatures of up to 42°C were expected and a new building method was developed. In addition to the single-line main tunnel, a parallel tunnel was built, with the tunnel centres separated by 17 m, through which pipes supplied fresh air to the builders in the main tunnel. It was envisaged that the parallel tunnel could be upgraded to a second running tunnel when required. The first Simplon Tunnel (19,803 metres in length) was built almost straight, with only short curves at the two tunnel portals.

On 24 February 1905 the two halves of the tunnel came together, they were out of alignment by only 20.2 cm horizontally and 8.7 cm vertically. Construction time was 7½ years, rather than 5½ years due to problems such as water inflows and strikes.


Operations commenced through the tunnel on 19 May 1906. Because of its length among other things, it has operated with electric traction rather than steam from the beginning. The official decision to use electricity was made only half a year before its opening by the then still new SBB. Brown, Boveri & Cie (BBC) were commissioned to carry out the electrification. They decided in 1904 to use the system being introduced in Italy of three-phase power of 3,400 volts at 15.8 Hz[1] using two overhead wires with the track acting as the third conductor. BBC had no electric locomotives and initially acquired three locomotives (RA 361 - 363) built for the Ferrovia Alta Valtellina—owner of the lines from Colico to Chiavenna and Tirano, which had been electrified with this system in 1901 and 1902[1]—from their owner, the Rete Adriatica railway company. These three locomotives hauled all traffic through the tunnel until 1908. On 2 March 1930 the Simplon tunnel was converted to single-phase alternating current system of 15,000 volts at 16.7 Hz.


Between 1912 and 1921, the 19,823 metre-long second tube, known as Simplon II, was built. On 7 January 1922 the northern section from the north portal to the 500 metre-long passing loop in the middle of the tunnel was brought into operation, followed on 16 October 1922 by the southern section from the passing loop to the south portal.

Second World War

During the Second World War, on both sides of the border there were preparations for the possible detonation of the tunnels. The explosives attached to the tunnel on the Swiss section were not removed until 2001. In Italy, the German army planned as part of its 1945 withdrawal to blow up the tunnel, but were thwarted by Italian partisans with the help of two Swiss officials and Austrian deserters.

Present and Future

Car-carrying shuttle trains

There is a car-carrying shuttle between Brig and Iselle di Trasquera. It provides a 20 minute train journey as an alternative to driving over the Simplon Pass.

The service was brought into operation on 1 December 1959. With the improvement of the Simplon Pass its frequencies steadily declined and it was abandoned on 3 January 1993. However, on 12 December 2004, services were resumed and trains now run approximately every 90 minutes.

Piggyback transport

At the beginning of the 1990s a project to implement the rolling highway system of piggyback operations for transalpine freight on the Lötschberg–Simplon axis was implemented. Such operations were possible under the existing profile of the Simplon Tunnel but capacity would have been heavily restricted. Its height was too low for the transport of trucks at the permitted maximum corner height of up to 4 metres. Therefore, the height of the tunnel was increased by lowering the rail line. The extremely complex work to lower the trackbed in the tunnel began in 1995 and lasted eight years. At the same time, the tunnel vault was rehabilitated, while the drainage tunnel had to be re-built. A total of 200,000 m³ of rock was removed with hydraulic (pneumatic?) hammers.

In addition, new railway electric traction system was installed using overhead electric rail instead of the tensioned cable normally used for overhead electrification so that the required 4.90 m height clearance could be achieved. In the late 1980s a one kilometre-long overhead electric rail had been tested at 160 km/h. Before this experiment trains running under overhead electric rail in Switzerland had been limited to 110 km/h and internationally to 80 km/h.[2]

Rail operations with restrictions were maintained during the entire construction period.

Expansion of access routes

In order to expansd the Lötschberg-Simplon axis into a powerful transit axis, various extensions to the access lines (from Bern and Lausanne in the north and from Novara and Milan in the south) have made in recent years and decades. The largest projects have dealt with the northern access from Basel-Bern via Lötschberg. Between 1976 and 2007 there were three major transformations. First, the remaining single track line between Spiez and Brig was dualled. Later adjustments were made to the tunnel profile for piggyback traffic; in places only widening one track was possible. Finally in 2007 the Lötschberg base tunnel opened, although part of this is still single in order to save costs.

Clearances were also raised for the piggyback traffic on the Italian side as well on the Simplon southern approach. Here, too, for financial reasons, at times only one line was cleared for the rolling highway. South of Domodossola the single line to Novara via Lake Orta was electrified and modernized.

The classic approach to the Simplon from Paris and Lausanne—but less important for today's transit traffic—was upgraded in the context of the nation-wide rail upgrading project, Rail 2000 between 1985 and 2004. Further adjustments are proposed. In November 2004, the 7 km-long new line between Salgesch and Leuk in the Rhone Valley was completed to replace the last single track bottleneck on the route. Under the ZEB ("Future rail development projects") package the maximum speed on the long straight sections of the Rhone valley lines will be increased from 160 km/h to 200 km/h.

Facts and Figures

  • Length of Tunnel I: 19,803 m
  • Length of Tunnel II: 19,823 m
  • Height of north portal, Brig: 685.80 m
  • Height of the crest of the tunnel: 704.98 m
  • Height of south portal, Iselle: 633.48 m
  • Slope on north side: 2 ‰
  • South slope: 7 ‰
  • Commencement of construction on north side: 22 November 1898
  • Commencement of construction of south side: 21 December 1898
  • Penetration: 24 February 1905
  • Inauguration: 19 May 1906
  • Operation of electrical operation: 1 June 1906

Spiral tunnel

On the rail line north from Domodossola prior to the Simplon tunnels is the 2968 meter "Varzo Spiral Tunnel," probably the longest spiral tunnel in the world. See the route diagram at the start of this subject.


  1. ^ a b Kalla-Bishop, P. M. (1971). Italian Railways. Newton Abbott, Devon, England: David & Charles. p. 98.  
  2. ^ "Erfolgreiche Stromschienenversuche im Simplontunnel (Successful track trials in the Simplon tunnel)" (in German). Die Bundesbahn (Darmstadt) (3). 1989. ISSN 0007-5876.  


  • Michel Delaloye (Hrsg.): Simplon, histoire, géologie, minéralogie. Ed. Fondation Bernard et Suzanne Tissières, Martigny 2005. ISBN 2-9700343-2-8 (in German)
  • Frank Garbely: Bau des Simplontunnels. Die Streiks! Unia, Oberwallis 2006 (in German)
  • Thomas Köppel, Stefan Haas (Hrsg.): Simplon – 100 Jahre Simplontunnel. AS-Verlag, Zürich 2006. ISBN 3-909111-26-2
  • Wolfgang Mock: Simplon. Tisch 7 Verlagsgesellschaft, Köln 2005. ISBN 3-938476-09-5 (in German)
  • M. Rosenmund: Über die Anlage des Simplontunnels und dessen Absteckung, in: Jahresberichte der Geographisch-Ethnographischen Gesellschaft in Zürich, Band Band 5 (1904-1905), S. 71ff. (Digitalisat) (in German)
  • Hansrudolf Schwabe, Alex Amstein: 3 x 50 Jahre. Schweizer Eisenbahnen in Vergangenheit, Gegenwart und Zukunft. Pharos-Verlag, Basel 1997. ISBN 3-7230-0235-8 (in German)
  • Georges Tscherrig: 100 Jahre Simplontunnel. 2. Auflage. Rotten, Visp 2006. ISBN 3-907624-68-8 (in German)
  • Enzyklopädie des Eisenbahnwesens. Bd 9. Urban & Schwarzenberg, Berlin 1921 Directmedia Publishing, Berlin 2007 (Repr.), S.68–72. ISBN 3-89853-562-2 (in German)

External links


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