As It Happens

To cross its fjords, Norway hopes to be first country to build submerged floating tunnel

The drive along the west coast of Norway is astonishingly pretty. It's also an exhausting commute of more than 20 hours, involving 7 fjord-crossing ferries. But the Norwegian government thinks it can reduce the drive time by half, with its ambitious plan for the world's first submerged floating tunnel.

The underwater tunnel would cut the 21-hour coastal commute by half, says chief engineer

Illustration showing open cross-section of the submerged tunnel. (Statens vegvesen/Vianova)


The Norwegian government has launched an ambitious and complicated plan to build the world's first submerged, floating tunnel along the country's west coast.

The bold design promises to cut travel time along Route E39 —  a highway connected by seven ferries with a current commute of 21 hours — by as much as half.

Arianna Minoretti is the chief engineer on the project. As it Happens host Carol Off spoke to Minoretti about the elaborate design. Here is part of their conversation.

Ms. Minoretti, that coastline of Norway is so beautiful, isn't it? Can you just describe what it's like to drive on that highway?

It's an experience that you have to do once in your life. It's a beautiful area, full of nature, water, and these fantastic fjords.

What you can feel driving there is — you know, this sensation that all these advertisement of cars try to to sell? This sense of freedom driving in the nature? Well, that's the place where you can feel it.

Illustration of the proposed submerged tunnel on Highway E39, on the west coast of Norway. (The Norwegian Public Roads Administration/Vianova)

But so, why would anybody rather spend that time driving in a tunnel or a tube under the water? I mean, how much faster could they travel that coast? 

The studies we have done — the Norwegian Public Road Administration has done — shows that there could be a reduction of half the time that is used nowadays to drive on that road.

And this is due mainly for the seven ferries that are present along the west coast of Norway. The submerged floating tube bridge is one of the possible structures that we are evaluating for several of these fjords.

And how long will these stretches of submerged bridge, these floating tunnels, how long will they be?

It can be several kilometres. For example, one of the latest studies we have done is for the Bjorn Fjord. And this was around five, six-kilometre crossing.

But we have also evaluated this structure for other crossings that are really shorter, like 600 metres, because the possibility of having this type of structure has, let's say, other process that a normal bridge it will not have.

Looking at pictures of this, it's extraordinary that you could have a floating tunnel like that with the braces above the water, the way it looks. Has this been done before? Is there another example of something of this nature that's already been built?

No. If we are going to build it, it will be the first in the world. But it's not a new structure, in the sense that the concept is an old concept.

It was proposed for the first time in 1882, I think, [by naval architect] Sir Edward Reed. But the technology obviously wasn't ready. In Norway, the concept was proposed [for] the first time in 1923, or something like this. And the Norwegian Public Road Administration started, let's say, early, to develop some of these studies.

But it's just with the studies along the E39 that this structure has been proven to be really feasible. And this is thanks to the experience that Norway has with the offshore and oil structures.
Map of Route 39 along Norway's west coast, from Kristiansand to Trondheim. (Statens vegvesen)

I was going to say that they do kind of look like those platforms — the same concept as the platforms for the oil industry. But this tunnel has to be below the surface far enough that it doesn't interfere with ships on top, and it can't be so low that it interferes with anything going underneath it, right?

Yeah. But these are all situations that are evaluated during the design. 

You have the pontoons that are floating on the water. So you could have a collision with a ship. But also underwater, some of these fjords are an area of practice for the Marine and Navy [Corps]. So you could have a collision with a submarine, for example. But all these are situations that are evaluated during the design. Everything is under control.

Artist rendering of a cross-section of the submerged floating tunnel. (Snøhetta)

All right, well we'll have to take your word for it. Because you're one of those engineers who's going to make that commitment to us. Just finally, one last question. It will still be possible, I presume, for people who want to drive that coastline and see that extraordinary scenery — that will still be possible, will it?

Of course. For some of these fjords we are already thinking to build some over-sea bridges. So in [those] areas they will pass in a year, let's say.

But anyway, the local transport would be would be maintained. So if you are on holiday, you can choose the longest road.

But if you're in a hurry, or you have to reach a hospital, obviously I don't think that you want to wait to see the scenery. You want to arrive as fast as possible. So yeah, there will be this possibility.

Interview produced by Zahraa Hmood. Q&A edited for length and clarity.


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