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.

From https://www.fhi.no/en/op/hin/population/life-expectancy/, life expectancy in Norway is about 82 years.

Together, that means the tunnel will save one human life in about 20 years, not taking into account pedestrians, or indeed realistic usage numbers.