The political decision

In 1869, the Trieste Chamber of Commerce had sent a petition to the Emperor Franz Joseph, in which they argued that the opening that year of the Suez Canal would indubitably lead to further development of Trieste, the main port of the Austro-Hungarian Empire; therefore, a second railway line to Vienna or the northern parts of Austria would be needed to support increased maritime traffic, in addition to the existing Austrian Southern Railway. The discussion regarding the path that new railway would take was not easily settled, and led to a "nearly thirty year long war".^[3]

Only by 1901 was this dispute settled. On 12 February of that year, the Minister for Railway Affairs of Austria Heinrich Ritter von Wittek brought a bill to the attention of the Imperial Council (the Austrian parliament) for the construction of and public investment in new railways. After approval by both chambers, the Emperor signed the bill into law on 6 June 1901.^[4] Among other provisions, the law provided that the Karawanks and Wocheiner (now Bohinj) railways should be built by 1905 as main lines of the first rank. The cost of that railway was estimated at 103.6 million Kronen, by far the most expensive railway project in the law. That cost would be covered by the issue of government bonds.

To overhaul such a large project, the Minister named a Construction Director directly subordinate to him, the engineer Karl Wurmb. In 1905, both Minister Wittek and Wurmb were subjected to criticism in parliament regarding cost overruns incurred by the construction because of geological difficulties.

On the Austrian Littoral side of the route, the builders first faced more demanding work in Podbrdo. Giacomo Ceconi’s company started the exploratory shaft along the axis of the planned Bohinj Tunnel as early as 1900. The works on the rest of the route for the Bohinj Railway was subcontracted in spring 1903. The section between Podbrdo and Šempeter was divided into nine parts: construction of the first five sections from Podbrdo to Ajba was taken over by the Viennese company Brüder Redlich und Berger, and the remaining four sections to Šempeter were taken over by the Italian company Sard, Lenassi & Co incorporated in Gorizia for this project by the Italian engineer Giovanni Battista Sard of Turin. onstruction of the section between Podbrdo and Grahovo was the most demanding: eight bridges, thirty-three culverts, and six tunnels had to be built because of avalanche slopes and watery terrain. The most important and still most admired structures along the entire Bohinj Railway are the Bohinj Tunnel, the Idrijca Viaduct at Bača pri Modreju, and the Solkan Bridge.^[5]

Operation until 1945

After the First World War, the railway was separated to Yugoslavia and Italy as a result of the Treaty of Versailles. The border had been located in the middle of the Bohinj tunnel; Italy obtained the whole area of the Isonzo valley. In Italy, the new Solkan bridge was reconstructed in its original form.^[6] The segment Villa Opicina–Trieste was until 1936 electrified with the 3000 V direct current.

Operation since 1945

In 1945, the border between Italy and Yugoslavia moved in the western direction; most parts of the Isonzo valley then belonged to Yugoslavia. Until 1948, the Kreplje–Sežana branch line was constructed; near Sežana it connects to the historical Austrian Southern Railway. This connection enables traffic between the Southern Railway and this line to avoid Italian territory altogether. At this time, the passenger service south of Kreplje ceased, terminating at Sežana instead of continuing into Italy. The original southern terminus, Trieste Campo Marzio, thereafter served only local passenger traffic, and entirely closed to passengers in 1960. Because of political isolation in Europe, the Bohinj Railway lost its importance from 1945 to 1990.

After the opening of the Koper Railway in 1967, services ran from Koper via the Karst Railway and this line into Germany or Austria. After the earthquake in Friuli in 1976, it was used as a detour for express trains.^[7] Since the beginning of the 1990s, rail transport has been mostly via Pivka and Ljubljana, which caused the Soča corridor to decline significantly.

The accession of Slovenia and other states to the European Union in 2004 and to the Schengen area at the end of 2007 significantly increased rail traffic from large parts of Europe to the ports of Trieste and Koper, which are conveniently located especially for the Czech Republic, southern Germany, Slovakia, Austria, and Hungary, by abolishing border controls. Nevertheless, international passenger services on the Bohinj Railway did not resume.