Long travel time

The usual drive from Kristiansand to Trondheim in Norway takes about 21 hours by car if travelling 48 kilometers per hour (30 miles per hour) on average. The route along highway E39 involves seven fjords which, in turn, requires seven ferry rides.

A $25 billion construction project is now aiming to reduce that travelling time to just 10.5 hours. Their goal is to install permanent crossings across the fjords by the year 2035. The fjords are wide and some are quite deep making building typical bridges across them impossible. Norway is planning on fording these waterways with something people have never seen before — a submerged floating bridge. In other words, it is a traffic tube submerged in around 30 meters (100 feet) of water.

Submerged tunnels

According to Arianna Minoretti, a senior engineer with the country's public roads administration, the project is not as crazy as it sounds. Based on their plans, Sognefjord may be the perfect candidate for the first construction. Sognefjord is 1.3 km (4300 ft) deep and 1km (3300 ft) wide. The structure would consist of two curved concrete tubes, each 1.2 km (4000 ft) long around 20 to 30 km (65 to 100 ft) from the surface.

Credit: Norwegian Public Roads Administration

Flotation devices or pontoons on the surface that are connected to trusses would hold the tubes and keep them stable. The tubes may also be bolted to the bedrock in the bottom to make it more stable. Minoretti says that driving through the tubes will be just like driving through any tunnel.

Experts say that the project is doable and it combines technology from other structures built before. The technology is not something new, but it definitely is cool.

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