That's not the only externality; another one is wear-and-tear on roads. In most countries, fuel taxes are used in part to pay for road and highway maintenance [1]. Certainly Norway's extensive, mountainous highway system is not free to build and maintain, and imo all road users should pay their share to fund it. You could have a direct per-km tax enforced via some kind of GPS unit, but that has privacy implications. Traditionally the fuel tax was a reasonable proxy, since vehicles used fuel in rough proportion to the amount of road traversed.

[1] In the U.S. the link is explicit: almost the entirety of the fuel tax is earmarked for highway construction and maintenance, https://en.wikipedia.org/wiki/Highway_Trust_Fund