Floating traffic tubes will cut travel time, Norway says

Norway has earmarked US$25 billion for an ambitious plan to construct the world’s first submerged floating traffic tunnels.

In a bid to reduce travel time on the 1100km stretch between Kristiansand and Trondheim, which currently means seven different ferries to cross the various fjords, the proposed system of floating concrete tubes could reduce the 21-hour journey to just 11.

If given the green light, Sognefjord will be the first of the seven fjords to benefit from the project which will see the installation of two 1219m-long concrete tubes, one for each direction of travel. On the inside, the submerged floating tubes will look the same as any other road tunnel, with two lanes and ventilation systems in place to release exhaust fumes.

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Externally, the tubes will be connected to each other via floating pontoons and, where weather or water-current conditions dictate, tethered to the fjord floor which can be up to 500m below.

The unusually deep and wide bodies of water are the reasons the Norwegian engineers were forced to come up with the idea of the unconventional roadway.

While the idea of a floating traffic tunnel seems futuristic, the theory behind the idea actually dates back to 250 BC. Otherwise known as an Archimedes’ Bridge which, like the ancient Greek mathematician’s principle states, if the weight of the object — in this case the concrete tubes — is less than the weight of the water it displaces, then it will be buoyant.

Using Archimedes’ Principle, how deep the tunnels will be submerged will be determined by the overall weight of the concrete tubes. Reports suggest the tubes will be buoyant approximately 30 metres below the fjord’s surface to accommodate cruise ships and other vehicles using the water.

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