Indeed, if we assume cyclists use the tunnel 100 days a year going both ways through it, thats saving each one nearly 60+ hours a year. If each one's time is worth $20, that is over a thousand dollars per cyclist per year - it only takes 9k cyclists to make the savings outweigh the costs in five years.
And assuming that this will increase the number of people who choose to bike instead of to drive, you can also add savings for all the remaining drivers who get a slightly easier commute.
Why only 100d/y while Norwegian works around 190d/y? In my experience people tends to have a “main” commute mode that they only turn away from in exceptional cases. Easier to live with habits that mixing your timetables every other day.
People might use cars or public transport instead of a bike to commute if there is heavy rain or snow. This is an important consideration in Bergen which is notoriously the rainiest city in Europe (it rains more than half the time).
One of the factors other replies haven't considered is that Norway routinely spends a lot on transport infrastructure, with cost-benefit just one of the factors. This project was relatively cheap compared to the constant building of tunnels for cars that happens across the country. A typical project costs many times more than this.
Per capita Norway is one of the highest spenders in the world, due to the size and low population density of the country. Even with all this spending, transport in some places, especially the north, is slow & inefficient. This has resulted in a high number of airports and Norwegians flying more than almost every other nationality.
Okay. Taking the 20min saved per ride from the article, and 300 rides that would otherwise take the longer route per day out of my ass, we get 100 hours saved per day. That's approximately 4 days saved per day.
Strange, I have never heard of a separate escape tunnel for a tram tunnel. Even German U-Bahn/S-Bahn (which I am most familiar with) tunnels usually just have a walkway beside the tracks that leads to the next station or emergency exit. But I guess that also depends on length between possible stations/exits, or it's due to newer regulations, or maybe it was a "mixed calculation" ("if we build a separate tunnel, it's more expensive, but it can also be used as a bike/pedestrian tunnel").
Subway tunnels usually aren't that far from the surface, even those that dive/rise between stops. So they just dot in a few emergency stairs to the surface if stops are too far apart. This tram tunnel however apparently is a shortcut through some mountain (because otherwise, the bike sibling wouldn't make much difference), so the emergency exit problem isn't easily solved by digging vertically.
The problem here is similar to underwater tunnels. Making an emergency exit straight up is not possible or too expensive.
In this case it is too expensive/unpractical as you would have to dig several hundred meters up a mountain. Also a tunnel going sideways is easier for those who can not walk. And this long stairs up could be a problem even to those who can walk.
For those who don’t know the tunnels goes through a 477m high mountain/hill and both ends are roughly at sea level.
It depends on the length of the tunnel, the traffic in the tunnel, and various other requirements.
Older tunnels the "walk away from the dead train" option was heavily used; but more often now they try to deal with "get away from the horribly burning dead train that will suffocate everyone".
$46M USD, to save cyclists 5.5km/20 minutes; that seems like a pretty good return.