129 Norway’s Floating Highway


Steep, icy mountains and deep fjords make western Norway famously scenic, but they also make life difficult for motorists. With seven ferries along the way, the almost 700-mile trip between the cities of Kristiansand in the south and Trondheim in the north typically runs about 21 hours — at an average speed of about 30 miles an hour.


The Coastal Highway Route E39-project is the largest infrastructure project in modern Norwegian history, and quite possibly the largest on-going road project worldwide, says Arianna Minoretti, Chief Engineer at the Norwegian Public Roads Administration.

But that could soon change. A $40-billion infrastructure project being planned by the Norwegian government aims to replace the ferries with bridges, conventional tunnels and what could be the world’s first “floating tunnel.”

The submerged roadway — essentially a pair of concrete tubes submerged about 100 feet below the water’s surface — would help cut the Kristiansand-Trondheim travel time almost in half while minimizing the environmental impact on the area.

Though the floating tunnel is buoyant, it isn’t actually floating. The tubes would be stabilized by cables tethered to the seabed or by pontoons floating on the surface at roughly 800-foot intervals. With most of the hardware far below the surface, the tunnel wouldn’t interfere with the movement of ships and boats and even submarines, said Arianna Minoretti, chief engineer for the Norwegian Public Roads Administration.


The new road will cut the route almost 50km shorter, and reduce travel time in half – to just 10 or 11 hours. The reduction in travel time will be obtained by replacing ferries with bridges and tunnels, in addition to upgrading a number of road sections on land. Sixty per cent of Norway’s export goods are produced on the west coast, so an efficient and predictable transport system will be a great benefit for the national economy. By connecting cities along the west coast we will also create new patterns of habitation. The new road will shorten the path to reach hospitals, jobs and schools. The E39 continues to Denmark, and hence connects Norway with southern Europe. Preliminary estimates show that the required investments and improvements will cost approximately NOK 340 billion.

Plans call for the floating tunnel to open to traffic in 2050. And while it might be the first structure of its kind, it might not be the last. Rønnquist said engineers in Italy and China are pursuing similar concepts.

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Kevin Chang, a professor of civil and environmental engineering at the University of Idaho, offered a similar assessment of the challenges involved in building such a tunnel. “At the end of the day, the engineering community tends to be on the conservative side,” he said. “But with novel ideas, somebody has to sort of stick their neck out to say: We think this is the best solution even though it’s unproven elsewhere.”

"When I started working with this type of structure, I felt really excited," says Minoretti, who came to Norway specifically to work on the E39 project. "You can be an engineer and live your [whole] life without having this chance."

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