Norway is pressing ahead with the construction of Rogfast, the world’s longest and deepest subsea road tunnel, a flagship component of the country’s ambitious ferry-free E39 coastal highway initiative.
The 27km twin-tube tunnel, which will plunge to a maximum depth of 392 metres below sea level, is designed to link the Stavanger and Haugesund regions in Rogaland county, eliminating two existing ferry crossings. Upon completion, the project is expected to shave approximately 40 minutes from the journey between Bergen and Stavanger, Norway’s second- and fourth-largest cities.
First approved in 2017, groundbreaking took place in January 2018. However, work was suspended in late 2019 after projected cost overruns triggered the termination of existing contracts and a comprehensive restructuring. Construction resumed in late 2021 under revised terms, with the Norwegian Public Roads Administration now forecasting completion in 2033 at a total cost of around Nkr25bn ($2.4bn), a significant increase from earlier estimates.
Skanska, the Swedish-listed construction group contracted for the 9km northern section — which includes the deepest segment — is employing advanced laser-scanning and “digital twin” technology to ensure the two tunnel headings meet within a 5cm tolerance, one of the tightest specifications globally.
“Precision at this level is not merely a technical achievement; it directly translates into lower material consumption, reduced waste and lower emissions,” noted Burkhard Boeckem, chief technology officer at Hexagon, the geospatial technology provider supporting the project.
Geological difficulties have proved considerable. At depths exceeding 300 metres below sea level, contractors have encountered substantial saltwater ingress, necessitating sophisticated grouting techniques to seal fissures in the bedrock before advancing further toward the 392-metre nadir.
Ventilation will combine longitudinal jet-fan systems with dedicated shafts to the island of Kvitsøy, where a novel underwater double roundabout — 260 metres beneath the surface — will provide access to Norway’s smallest municipality.
Rogfast forms a critical part of the broader E39 upgrade, a 1,100km route currently interrupted by seven ferries that extends driving time between Trondheim and Kristiansand to 21 hours. The long-term objective, unlikely to be realised before 2050, is a continuous fixed-link highway that would halve that duration.
While the closure of ferry services will result in job losses in that sector, proponents argue that improved connectivity will unlock broader economic benefits, particularly for the region’s dominant aquaculture and energy industries, by reducing logistics costs and enlarging labour-market catchment areas.
Upon opening, Rogfast will eclipse the undersea portions of Japan’s rail-only Seikan Tunnel (23.3km) and the Channel Tunnel (37.9km) to claim the title of the longest road tunnel beneath the sea, while remaining far deeper than either.
In an era of tightening public budgets and heightened environmental scrutiny, the project underscores Norway’s willingness to deploy substantial sovereign wealth — funded indirectly by its vast oil and gas revenues — on transformative infrastructure that prioritises long-term regional integration over short-term fiscal restraint.
