High-speed rail line Venezia – Trieste – Ljubljana

Construction of a high-speed rail line (HSL, TAV), from northern Italy to Ljubljana, is official policy of the Italian and Slovenian governments. It is considered part of the Trans-European Networks (TEN) which are partly funded by the European Union. Specifically, it is part of TEN Priority Axis 6, and the earlier designated Pan-European corridor V. Neither specifies exact routes, but a link to to the port of Koper is included on both. Any such line will inevitably pass Venezia-Mestre (the mainland station of Venice), so the line can be considered here as a Venezia – Trieste – Ljubljana line.


The line from Venezia would parallel the A4 motorway and the existing line, along the flat coastal plain. Near Trieste, however, there are two major problems. The first is the geography of the city: it is easily approached from the direction of Venezia, but construction of rail lines in any other direction is very difficult. Trieste lies at the edge of the Kras (Karst) Plateau at 450-500 m, and any line must climb from sea level.

Click to enlarge: the vertical axis is exaggerated on these images…


The location of Trieste Centrale station, north of the city centre on the ‘Venetian’ side, reflects this differential accessibility. The old Austrian line into Trieste used a long zigzag along the plateau edge, to descend from Villa Opicina (on the plateau). The line (via Aurisinia junction) is about 25 km long, although the two stations are less than 5 km apart. What’s more, Trieste is not located between Venezia and Ljubljana. A HSL via Gorizia / Nova Gorica and the Vipava valley, would be 20-25 km from Trieste, at its closest. The second problem is political, but related to the geography. As with all TEN projects, national governments try to divert funds to improve their internal infrastructure. The priority of the Slovenian government is to improve access to the Port of Koper, in direct competition with the port of Trieste. It sees the new line to Trieste as a branch of a new Ljubljana – Koper line, implying that the line would approach Trieste from the south-east. The Italian government sees the new line as a link from northern Italy to central Europe – and has no interest in improving access to Koper. The resulting dispute has delayed the project.

Three options for the route near Trieste are under official consideration. There are (low-quality) maps of the three, at the end of the Province of Gorizia Transport Study. The first passes Monfalcone, at the head of the Gulf of Trieste, and then enters tunnel toward Villa Opicina, on the plateau. From there, it would run in tunnel to the Vipava valley, and again in tunnel to the Ljubljana Basin. This option by-passes Trieste entirely. A second option is a more northern tunnel, surfacing north of Villa Opicina, and then following the motorway to Divača. This variant is even further from Trieste. The third is the Slovenian government’s Koper line variant. For this variant, there are detailed alignment proposals: see the map in Nova železniška povezava Trst – Divača. The routes to Trieste (red, purple, green, orange) are clearly secondary to the Koper line (blue). That way, the EU contribution to an internal Slovenian project is maximised. However, even in this variant, the line would still not pass through Trieste Centrale station. (The link shown on that map in orange, would have an impossibly steep gradient). The map certainly shows how difficult it is, to connect the plateau (Divača at 435 m) to the coast,

The difficult route options illustrate a fact of geography: a through line Venezia – Trieste – Ljubljana is almost impossible. However, it is not necessary either. Services from the Venezia direction can simply be split: some to Trieste, and some to Ljubljana. The only problematic service is between Trieste and Ljubljana, with an unavoidable climb to/from the plateau. That suggests a solution similar to the existing configuration: trains from Venezia either stop at Trieste, or run through Villa Opicina station to Ljubljana. An optimum solution should also take account of another high-speed line – to Rijeka, parallel to the Ćićarija range. At Rijeka, it would connect with the planned high-speed lines toward Zagreb and Split.

The preferred option at Trieste would therefore be a plateau station, accessible by new lines from Venezia, Ljubljana and Rijeka. Although it could be located at several places near the plateau edge, such as Trebiciano or Padriciano, the best site for the new station seems to be the existing station at Villa Opicina. It allows easy connection with the existing lines: two lines down to Trieste, the existing lines from Venezia and Ljubljana, and the secondary transalpine line to Nova Gorica and Villach. The station zone at Villa Opicina has enough room for expansion.

Click to enlarge: Villa Opicina station…

Villa Opicina station

Approaching Villa Opicina from the Venezia direction, the new line can make use of the topography. The plateau edge slopes downward toward Monfalcone: the new line can use this easier gradient. It would run alongside the motorway, and roughly parallel to the existing Aurisinia line, climbing 300 m from Monfalcone (an average gradient of 1,5%).

Click to enlarge…


From Villa Opicina station, the Rijeka line could run across the plateau (north of Lipica and south of Lokev), and turn south past Rodik, to the line of the Rijeka highway. Its alignment is not treated further here.

Click to enlarge: Possible alignment of the Rijeka HSL…

Possible alignment of the Rijeka HSL

The new Ljubljana line would also begin at Villa Opicina station, and run parallel to the motorway to Divača, passing Fernetti and Sežana. In about 15 km, it would climb 125 m. (Except for the Vipava route, all official proposals assume a route through Divača, but they do not specify use of Villa Opicina station).

Click to enlarge…


From Divača at 435 m elevation, the motorway climbs 220 m to the Postojna basin (540-560 m). It passes two ridges, with the village of Senožeče lying between them. A single tunnel of about 10 km, seems the only option for a rail line here: that is the scenario in the official proposals. On the map below, the old line is highlighted in green, and the tunnel is shown schematically (red dotted line). From the Postojna basin at 550 m, the line would descend to the Ljubljana basin at about 300 m. This too is the officially proposed alignment – either in a single tunnel, or surfacing briefly in the Planina basin / Planinsko polje, at 450 m elevation (red dashed line).

Click to enlarge: The base map is an Austro-Hungarian military map of around 1910, with German spellings.

Click to enlarge: the topography of the basins...


The solution for service of Trieste itself, from Villa Opicina, is probably a completely new line on a new system. From Villa Opicina at 310 m, to Trieste Centrale at 10 m, the distance is 4400 m, and the gradient over a straight line is 7%. It is no longer necessary to think of rack railways, since modern rubber-tired light metros, such as the VAL, can climb gradients of up to 10%. Since the ground rises from the Trieste centrale station, the line can probably take the form of a straight tunnel.

Click to enlarge: the two stations of Treiste, and the ridge at the edge of the plateau…

The two stations, and the ridge at the edge of the plateau

This solution has a historical precedent: in 1902, a combined tram-funicular line was built. (It is still in use, but primarily as a tourist attraction). A light metro should take about 6-8 minutes for the journey between the two stations.

High-speed rail line Venezia – Trieste – Ljubljana

One thought on “High-speed rail line Venezia – Trieste – Ljubljana

  1. […] High-speed rail line Venezia – Trieste – Ljubljana « Infrastruct By infrastruct From there, it would run in tunnel to the Vipava valley, and again in tunnel to the Ljubljana Basin. This option by-passes Trieste entirely. A second option is a more northern tunnel, surfacing north of Villa Opicina, … That way, the EU contribution to an internal Slovenian project is maximised. However, even in this variant, the line would still not pass through Trieste Centrale station. […]

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