Trans-Alpine high-speed route via Splügen base tunnel

Trans-Alpine HSL with Splügen base tunnelA rail tunnel under the Splügen Pass is a long-standing proposal, supported by local interests in eastern Switzerland. (Road and rail tunnels have been proposed for all major Alpine passes). A Splügen base tunnel was considered by the Swiss federal government in the 1980’s. The decision was to use the the Gotthard and Lötschberg axes instead. Those base tunnels are under construction, as part of the resulting AlpTransit project (in German NEAT, or Neue Eisenbahn-Alpentransversale). See the list of transalpine rail corridors.

A Splügen base tunnel could form part of a new high-speed route, from Stuttgart to Milan (Milano), nearly 500 km long. With a new rail link from the Allgäu, roughly parallel to Autobahn 96, it would also be an alternative route between Munich (München) and Milan. It would also shorten some other routes, in comparison with the Gotthard axis: see Splügen-NEAT for examples.

A Splügen base tunnel would run from Thusis to Chiavenna, about 45 km long. However, that still leaves 90% of the high-speed route to build. In that perspective, the tunnel itself is a relatively simple project. It has no conflicts with topography and urban areas. Other sections are more problematic. For instance, there is already a rail line from Chiavenna to Milan, but about half of it is single-track. It follows the winding shore of Lake Como / Lecco, which is also heavily urbanised. To avoid this section a new line is needed, from the Plain of Chiavenna to south of Lecco. Most of it would be in tunnel, and these tunnels would probably be longer in total, than the Splügen base tunnel.

Bellano station, on the Chiavenna – Lecco line, image under CC licence by ev0ev0.

Bellano station on Chiavenna rail line along Lago di Como

It is not possible to describe such a huge project in detail here. (Some sections will be covered in more detail later). The proposal is a high-speed route, consisting almost entirely of new high-speed lines (HSL) on new alignments. Some HSL sections would follow existing lines, but preferably no tracks would be shared with local services, except at main stations.

The route can be broken down into the following components:

  • a new high-speed line Stuttgart – Ulm (Neubaustrecke, NBS). This is an officially planned line, but linked to the controversial Stuttgart 21 project. It would shorten the route between the two cities, to about 85 km.

NBS Stuttgart – Ulm, public domain image by Stoeffler.

  • a new HSL from Ulm to Memmingen, starting very near Ulm Hauptbahnhof, parallel to the existing Illertalbahn.
  • a new HSL line Munich – Memmingen, roughly parallel to Autobahn 96. It would closely follow the existing Allgäubahn to Buchloe.
  • a new HSL line from Memmingen south to Lake Constance (Bodensee), possibly alongside Autobahn 96, although that is not the shortest possible alignment here.
  • a new rail line through Bregenz, at the eastern end of the lake. The line would serve a new station here: the existing station has a restricted lakeside location, on a curving line.
  • a new HSL south along the floor of the Rhine valley, which gradually narrows from about 10 km at the lake, to 2 km at Chur. It could follow existing lines on either side of the river, so there might be a high-speed line through Liechtenstein. The line would in any case have a station, serving that section of the valley.

There would also be a station at Chur, the only regional centre in the mountainous interior of Switzerland, and the centre of the Rhaetian Railway network. Assuming that all trains would stop at Chur, the new line could run on the existing alignment, on viaduct.

Chur from the east, image under CC licence by Groeberman.

Chur from the east, Rhine valley

After Chur, the new line would turn into Hinterrhein valley, to a tunnel portal near Thusis. (South of here, the valley is too narrow for a surface line anyway). The following sections are:

  • the Splügen base tunnel itself
  • a tunnel portal near Chiavenna, opening out into the Plain of Chiavenna. There would be another station here, serving the valley.
  • a new HSL south along the Mera valley, with a tunnel bypass of the Lago di Mezzola.
  • a HSL in base tunnel, or flank tunnels alongside the main lake, the Lago di Como and Lago di Lecco (these are one lake). The new line would start after crossing the Adda river near Cólico, and extend to Lecco, or just south of Lecco. (The new road along the lakeshore, the SS36, has a long series of flank tunnels).
  • a new HSL parallel to the existing 50-km line, from Lecco through Monza to Milan. Near Lecco, the Lecco – Monza line has recently been realigned, but is still too curved for a HSL alignment. Several new tunnels would be needed here too. About 10 km from Lecco, the line enters the Lombardy plain. The main problem here is the restricted alignment. The Milan – Monza line was built in 1840, as a almost straight line, but it has been shifted since then, and is now surrounded by buildings. The whole region is intensively urbanised, making it difficult to add tracks, or improve curves.

Stuttgart and Milan have roughly comparable urban regions, each with about 2-3 million inhabitants, depending on definition. The comparable Munich region has about 2.5 million inhabitants. The new trans-Alpine route would link these three regions.

It would also carry trans-Alpine traffic from urban regions in Switzerland, notably Zurich. The difference is that Zurich has an alternative route to Milan, via the old and new Gotthard tunnels. That applies to traffic from a much wider area, for instance from north of Basel, or from south of the Po: fro such traffic, the Splügen route is one of several alternatives.

Ulm and Monza are the only intermediate cities on the route, each with about 120 000 inhabitants. (Monza is within the Milan agglomeration anyway). Otherwise, there are only large and medium-sized towns. Lecco, with 50 000 inhabitants, is the largest of them, but the alignment might bypass it.

The new Stuttgart-Ulm line would be 85 km long, and the HSL Ulm – Memmingen about as long as the existing line, 52 km. The route from Memmingen to Chur would be approximately 150-160 km long, depending on the alignment. The Chur-Lecco section would be about 120 km long, assuming that the geology permits straight base tunnels. With more flank tunnel sections, it could be up to 30 km longer. The Lecco – Milan section will equal the existing line, at 50 km.

The Stuttgart – Milan route would be about 450-490 km long, in total. The connecting Memmingen – Munich HSL would be 110-115 km long. In total the trans-Alpine route would be around 600 km long, reaching an altitude of 700 m near Thusis. For comparison: China is building a high-speed rail line from Lanzhou to Urumqi, 1776 km long, over the Qilian Mountains, with a maximum elevation of 3858 m. Compared to that, no new trans-Alpine routes are ‘beyond construction’.

Trans-Alpine high-speed route via Splügen base tunnel

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