Construction

A monument in memory of the deceased workers of the Simplon Tunnel was erected next to the Iselle di Trasquera railway station on 29 May 1905.

The construction of the tunnel was carried out by the Hamburg engineering company Brandt & Brandau, of Karl Brandau and Alfred Brandt. On average, 3,000 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 2,150 m (7,054 ft) of rock over the tunnel, temperatures of up to 42 °C (108 °F) 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 (56 ft), 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 m (64,970 ft) 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 202 mm (8 in) horizontally and 87 mm (3.4 in) vertically. Construction time was 7+1⁄2 years, rather than 5+1⁄2 years, due to problems such as water inflows and strikes.

Art Nouveau Silver Medallion by Giannino Castiglioni for the Milan International Exhibition 1906. The South Portal of the Simplon Tunnel is on the obverse.

Electrification and operation

Old poster for the train between Paris and Milan (from 1908, two years after opening. Note the double-tracked depiction – in reality, a second single-track tunnel only opened in 1912).

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 three-phase system being introduced in Italy, with a three-phase power supply of 3,400 volts at 15.8 Hz^[5] using two overhead wires with the track acting as the third conductor. BBC had no electric locomotives and initially acquired three locomotives built for the Ferrovia della Valtellina—the owner of the lines from Colico to Chiavenna and Tirano, which had been electrified with this system in 1901 and 1902^[5]—from their owner, the Rete Adriatica (Adriatic Network) railway company. These three locomotives (which became FS Class E.360) hauled all traffic through the tunnel until 1908. On 2 March 1930, the Simplon tunnel was converted to 15 kV, 16.7 Hz AC (single-phase).

Expansion

Between 1912 and 1921, the 19,823-metre long (65,036 ft) second tube, known as Simplon II, was built. On 7 January 1922 the northern section from the north portal to the 500-metre long (1,640 ft) 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 was thwarted by Italian partisans with the help of two Swiss officials and Austrian deserters.

North portal

South portal

South portal at Iselle di Trasquera railway station. The picture was taken through a loophole of an old Italian World War II bunker. The bunker's weapons were directed to the tunnel's south portal.

Car-carrying shuttle trains

A car transport train arriving in Iselle di Trasquera railway station

There is a car-carrying shuttle between Brig and Iselle di Trasquera, which provides a 20-minute train journey as an alternative to driving over the Simplon Pass. The service began on 1 December 1959. As roads over the Simplon Pass steadily improved throughout the 1970s and 1980s the tunnel's shuttle schedule was cut back, then ended altogether on 3 January 1993. Almost twelve years later, on 12 December 2004, the car shuttle service began again and now runs about every 90 minutes.

Piggyback transport

In the early 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 previous profile of the Simplon Tunnel, but capacity would have been heavily restricted because its height was too low to carry trucks at the permitted maximum corner height of four metres (13 ft 1+1⁄2 in). The clearance in the tunnel was therefore increased by lowering the rail trackbed. This work began in 1995 and lasted eight years. At the same time, the tunnel vault was rehabilitated, while the drainage tunnel was rebuilt. A total of 200,000 m³ (260,000 cu yd) of rock was removed with pneumatic breakers.

In addition, a new railway electrification system was installed using overhead electric rail instead of the tensioned cable normally used for overhead electrification so that the required 4.90-metre (16 ft 7⁄8 in) height clearance could be achieved. In the late 1980s, a one kilometre (0.62 mi) long overhead electric rail had been tested at 160 km/h (99 mph). Before this experiment, trains running under overhead electric rails in Switzerland had been limited to 110 km/h (68 mph) and internationally to 80 km/h (50 mph).^[6]

Restricted rail operations were maintained during the entire construction period.

Expansion of access routes

In order to expand 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 been 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, the Lötschberg Base Tunnel partially opened in 2007, although the new tunnel still has a 21-kilometre (13 mile) single-track section; this was done in order to save costs for the construction of the longer Gotthard Base Tunnel, which was completed in 2016.

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—less important for today's transit traffic—was upgraded in the context of a nationwide rail upgrading project, Rail 2000, between 1985 and 2004. Further adjustments are proposed. In November 2004, the 7-kilometre long (4.3 mi) 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 to 200 km/h (99 to 124 mph).

2011 fire

On 9 June 2011, a 300 m (984 ft) section of the Simplon II tunnel's roof was seriously damaged when a northbound BLS freight train caught fire and stopped 3 km (1.9 mi) into the tunnel. The temperature exceeded 800 °C (1,470 °F) and took more than two weeks to cool back to normal. By agreement all repairs to the tunnels are the responsibility of the SBB, which expected to reopen the tunnel in December 2011. The other tunnel remained in service.^[7]

Repair work was completed in November 2011.^[8]