Reconstruction of the Sozina railway tunnel—almost 70 years old and the longest in Montenegro—could begin after 2027, as €850,000 worth of structural testing and project documentation will be carried out until then. The tunnel upgrade is part of the Golubovci–Bar railway reconstruction, aimed at meeting European railway standards.
The Railway Infrastructure of Montenegro (ŽICG) told Vijesti that it received a grant through the Western Balkans Investment Framework (WBIF) and support from the European Investment Bank (EIB) for this work. They noted that the 6,170-meter “Sozina” tunnel does not currently meet modern EU efficiency, regulatory, and technical requirements, including Technical Specifications for Interoperability (TSI).
ŽICG stated that its goal is to align the tunnel with the highest possible TSI standards following the planned modernization. The €850,000 grant will finance geotechnical, geodetic, and structural investigations to determine the true condition of the tunnel and define the necessary rehabilitation measures. The project is expected to be completed by February 2027, after which tenders for construction and rehabilitation will be launched as part of the wider Podgorica–Bar railway reconstruction.
Monitoring of the project is being conducted by JASPERS, the EIB, and the EU Delegation in Montenegro to ensure compliance with EU procedures. The company SUEZ Consulting has been engaged to carry out investigations and prepare technical documentation.
Annual traffic: 11,000 trains
ŽICG explained that the investigations will determine load-bearing capacity, lining conditions, and drainage system performance. These results will define the required rehabilitation measures to improve safety and long-term stability. The data will form the basis for the project documentation, enabling more reliable and efficient railway traffic between Bar and Vrbnica.
The cleaning of the tunnel vault using high-pressure equipment is nearing completion, enabling visual inspection and identification of defects. Detailed investigations will follow, including geological and geotechnical testing, geo-radar scanning, and thermographic analysis. Future work scope and timelines will depend on these results, technical constraints, and cost assessments.
Around 30 trains per day—approximately 10,950 annually—pass through the tunnel. The current operating speed is 80 km/h, with a 60-meter section limited to 30 km/h.
Historical context
“Sozina” was built in the late 1950s as part of the Belgrade–Bar railway, with the Podgorica–Bar segment constructed after World War II. The aim was to build a modern standard-gauge line that would reduce travel time between Titograd (Podgorica) and Bar to about one hour—nearly seven times faster than the old narrow-gauge line, which required train transfers and even a boat crossing of Lake Skadar.
Construction across the entire section was delayed due to the difficult excavation of the Sozina tunnel, which faced challenging geological conditions, limited machinery, and extensive manual labor with explosives.
Longest tunnel on the Belgrade–Bar line
ŽICG said it does not have complete records of all contractors, except that the company Tunelogradnja Beograd and numerous youth brigades from across former Yugoslavia took part in the construction. The Podgorica–Bar section was officially opened on 29 November 1959.
The tunnel is 6.17 km long, with an internal height of 6.4 meters and width of 4.5 meters, making it the longest tunnel on the Belgrade–Bar railway. For comparison, the old narrow-gauge line between Bar and Virpazar had 43.3 kilometers of track with steep gradients and numerous curves, while the straight-line distance between the two towns is only 18 km. Today’s railway between them is 20.7 km long.
During decades of operation, the tunnel has suffered damage due to being located in a seismically active zone, including cracking and flooding. Reconstruction projects were carried out in 1970, 1982, 2010, and 2016, with major works executed in 1972, 1982, and 2017.
Between 1962 and 1980, water infiltration was monitored, and in 1982 the company ZGP Sarajevo built a drainage tunnel to prevent flooding. The most significant upgrade came in 2017 under the EU’s IPA III program, which included reconstruction of the track bed, replacement of wooden sleepers with concrete ones, and installation of new rails and ballast.
These works cost €4.08 million, with supervision costing an additional €134,000, resulting in increased train speeds and making Sozina the only railway section in Montenegro equipped with concrete sleepers.
