Norway is redefining underwater driving with a tunnel so vast it even features its own roundabout.
Have you ever driven through a tunnel that felt endless? Think beyond the Holland or Battery tunnels in the U.S.—Norway is now building the world’s longest undersea car tunnel: a 17-mile stretch linking Stavanger in the south to Haugesund in the north. Remarkably, the route also reaches the island of Kvitsøy, which will be connected via a submerged double roundabout.
Rogfast, the project’s name, will consist of two parallel tunnels, each carrying traffic in a single direction per tube. What stands out isn’t just the length, but the engineering concept of the roundabout beneath the waves. While most people find roundabouts challenging on land, Norwegian planners are confident drivers can navigate this 850-foot-underwater junction when finished, a claim supported by coverage from CNN.
But this tunnel isn’t only long—it’s also deeply buried. Designed to replace several ferry routes, Rogfast will be the longest submerged car tunnel in the world. Its depth will reach about 1,286 feet below the sea surface at its deepest point, far below ordinary roadways. The pressure involved is immense: estimates show seawater pressure rising from around 437 psi at current depths to more than 570 psi at maximum depth.
The project’s progress is equally ambitious. Two construction teams are working from opposite ends—one from the north and one from the south—with the aim of meeting in the middle with less than two inches of clearance on either side. It’s a bold undertaking that underscores Norway’s willingness to push infrastructure to previously unimaginable extremes.
Controversy and curiosity aside, Rogfast illustrates how nations are rethinking underwater transport. Could such audacious engineering become a blueprint for future tunnel networks, or will the challenges prove too daunting as depths increase? Share your thoughts on whether this kind of mega-tunnel is worth the investment and what implications it might have for traffic, maintenance, and coastal communities.
