Norway’s E39 Rogfast: longest undersea road tunnel

December 05, 2025

Norway is advancing one of the most ambitious infrastructure projects ever attempted—a 17-mile (26.7 km) twin-tube undersea tunnel, soon to hold the title of the world’s longest and deepest road tunnel beneath the sea floor. Designed with long-term durability, reduced emissions, and environmental stewardship in mind, the Rogfast megaproject marks a milestone in green Scandinavian engineering.

The construction contract, valued at roughly USD 495 million (NOK 5 billion), was awarded to the Swedish engineering leader Skanska AB by The Norwegian Public Roads Administration. The work forms part of a national effort to develop cleaner, faster and more nature-aligned transport solutions.

A new ferry-free link between Stavanger and Bergen

Rogfast will carve a direct, ferry-free route beneath Norway’s dramatic coastal landscape, dramatically reshaping travel between Stavanger and Bergen. Once open, the tunnel is expected to reduce journey times by up to 40 minutes, improving logistics, reducing idling emissions from ferry transport, and supporting more eco-efficient traffic flow along the west coast.

Stretching to a depth of 1,280 feet (390 meters) below sea level, the tunnel will create a robust and climate-resilient transport corridor built to withstand pressure, seawater environments, and decades of use.

A core component of the E39 green coastal highway

As part of the expanding E39 highway system, which extends 830 miles across Norway and Denmark, Rogfast is positioned to become a key pillar in a future-proof transport network. The route strengthens the West Coast corridor connecting Kristiansand, Stavanger, Haugesund and Bergen, enabling better commerce, tourism and emission-reduced mobility.

Construction initially began in 2018 before pausing due to increased costs and scope revisions, later restarting in 2021 with a stronger financial and technical framework. The megaproject is projected for completion in 2033, with a final estimated cost of NOK 25 billion (USD 2.4 billion). Despite delays, the long-term vision remains unchanged: cleaner travel, greater connectivity and improved environmental efficiency.

The tunnel will consist of two parallel tubes, each containing two traffic lanes, along with emergency passages and safety-enhanced escape routes engineered to modern ecological standards.

One of its most unique features is a massive underground double roundabout, located 260 meters (853 feet) beneath the ocean, enabling direct access to Kvitsøy—Norway’s smallest municipality.

Europe’s deepest and most technologically precise tunnel

Building Rogfast requires unprecedented precision. Engineers rely on advanced laser-guided alignment scanners to ensure excavation accuracy within a margin of just five centimeters (1.97 inches). These technologies create a live digital twin of the tunnel, allowing sustainable planning, predictive analysis and early detection of structural inconsistencies—reducing waste and rework.

Working deep below sea level brings significant challenges, from extreme rock pressure to high-salinity water intrusion. To protect workers and preserve long-term tunnel integrity, engineers have developed innovative grouting, sealing and waterproofing solutions suited for deep-marine geology.

Air quality inside the tunnel will be maintained by a state-of-the-art longitudinal ventilation system powered by jet fans, supported by an air shaft linked to Kvitsøy—filed as an example of eco-driven ventilation design.

Although initial projections placed completion much earlier, current expectations extend toward 2050, reflecting the extreme complexity and safety demands of deep-ocean construction.

 “We are now 300 meters below the seabed and have already encountered considerable saltwater inflow,” said project manager Anne Brit Moen.
“As we progress to nearly 400 meters beneath the ocean, maintaining secure, low-impact working conditions remains our top priority.”

Rogfast: a tunnel built for future generations

More than an engineering milestone, Rogfast represents Norway’s commitment to sustainable mobility, reduced emissions and resilient coastal infrastructure. Once complete, it will stand as a global model for environmentally responsible megaprojects—built to last, built to connect, built for the planet.