Norway is building the world's longest and deepest subsea road beneath its fjords

Euronews

09-04-2025

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Norway is building the world's longest and deepest underwater tunnel, one of Europe's most ambitious engineering projects which is hoped will boost the country's transport links and infrastructure.
Running under the country's fjords, the record-breaking Rogaland fixed link - or Rogfast - will be about 26.7 km long and 390 m at the deepest point under the sea.
Once completed in 2033, the tunnel link will reduce the travelling time between two of Norway's largest cities, Stavanger and Bergen, by 40 minutes.
The Rogfast project, whose construction is nearing the halfway point, is part of the main European E39 highway, which runs along the west coast of the Nordic country.
Linking cities like Kristiansand, Stavanger, Haugesund and Bergen, it will also replace ferry crossings and make travel smoother, according to the Norwegian roads authority which is behind the project.
"Stavanger is the fourth-largest city in Norway, and Bergen is the second largest, so we hope that it's possible that this project will be able to reduce travelling time for workers as well when they are travelling to either Stavanger or Bergen on a daily basis," Oddvar Kaarmo, project manager of the Rogfast project at the Norwegian Public Roads Administration, told Euronews Next.
An island roundabout
One of the key design features of the new subsea highway is around the midway point where a spur connects the island of Kvitsøy, Norway's smallest municipality, to the main tunnel in the rock beneath it.
The Rogfast tunnel will feature two lanes of traffic in each direction. Under Kvitsøy, the lanes meet via two roundabouts that are being built 260 m below sea level.
"We have produced roundabouts in the tunnels before. But this might be one of the earliest constructions where we have this cross-section area with two roundabouts in the tunnel. As far as I know, I haven't seen two roundabouts in a cross-section area in a tunnel before," Kaarmo said.
The two roundabouts under the island will allow traffic to flow even when one of the lanes is closed.
"If something happens and we have to shut down a part of the tunnel, we can still run the tunnel by using one pipeline and traffic in each direction in one pipeline," he added.
The twin tube structure is also a safety measure.
"If a lorry or a truck [catches] fire in front of you and you are not able to turn around and drive out, you can just seek these green doors with exit signs… and you will be able to walk to the other pipeline of the tunnel. And we have this camera system that [allows us to] know exactly where you are. And we can pick you up and take you out of the tunnels," Kaarmo told Euronews Next.
Norway's tunnel building finesse
The Rogfast project, which is being built in parts at a cost of 25 billion Norwegian Krone (€2 billion), is currently half completed after ground was broken in 2018.
"In the north side, about 65 per cent of the tunnel is produced and then it's just the production of the tunnel like the drilling and blasting. And at the south end at Randaberg, it's about 45 percent [complete]," Kaarmo said.
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Unlike the Fehmarn belt fixed link currently under construction between Germany and Denmark that uses modular building method, Rogfast is being blasted and drilled straight through solid bedrock, a method Norway uses to ensure stability and durability under water pressure.
"You are travelling through solid rock. We have this distance between the roof in the tunnel to the bottom to the sea. Our regulations demand 50 m. So you're travelling at the sea bottom. We have subsea road tunnels which have that construction. And the new tunnel between Germany and Denmark, there they are laying down cases and put the cases together and they do not go under the bottom like we do in Norway," Kaamor said.
"In Norway, we produce tunnels quite cheap, if you compare it to a bridge for instance. And we have about 40 subsea road tunnels in Norway, and we are familiar with the construction. So normally it's easier and cheaper to build a subsea road tunnel than a bridge to the same island," he added.
The Rogfast fixed link is scheduled to be completed by summer 2033.
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"It will help the producer of seafood production to reach the market in a better way without ferries," Kaarmo said.
"It will see working travellers, industry, and probably also tourism. Because the west coast of Norway is a part of Norway that tourists often seek. For instance, Bergen. We have lots of tourists in Bergen. And when we have this road project which will allow us to travel to Bergen in a shorter time, most likely, the tourists will also get eyes for this part of Norway even more than today," he noted.
The Norwegian roads authority estimates 13,000 journeys will be every day for the new tunnel by 2053.
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