>the cost to society of trips by car is close to one euro per kilometre

I would like to understand what this means.

I don't have any idea if it's accurate or not but the implications make me think it requires some explanation.

If the true cost of travel by car is about one euro (currently $1.08?) per km, then - using ~4.7L / 100 km mileage of my car - by my arithmetic gas should cost on the order of 20 euros per liter to internalize the costs to society.

Some very brief research indicates to me that Danes price gas in DKK, but converted it's around 2 euros a liter.

So is Danish gas underpriced by as much as 10 times?