You used to have to take a large detour to get to Klaksvík - which is the second largest town - from Tórshavn (the capital). By taking the tunnel, you shave off 27 minutes.

Travel time to almost all of the north-eastern islands, and the towns on these islands, has been cut down by half an hour.

It is also safer. They also argue that it is cheaper, but I don't know about that.

Ignoring industry, that's just quality of life.

But consider a car accident; the ambulances have to get there in a hurry. Minutes might save lives here.