That makes sense to some degree, given that the taxes were meant for maintenance of roads. However the per mile tax should also be a sliding value based on vehicle weight as that increases damage to the road. So a light car going a few miles wouldn't be taxed as heavily as a truck going a long distance since it wouldn't damage the roads the same way. Though at the point you've thrown out any incentive for more fuel efficient ICE powerplants.
farmers and others also may drive quite a lot in vehicles on their own properties without ever touching a road. If it's purely for roads and not, say, including a carbon tax or something, that seems rather unfair.
Existing gas taxes also affect them in this way then. They pay for the gas tax used and they're not driving on public roads, so that seems to be a wash.
We actually have off-road diesel for this. Alberta also used to have "purple gas" but it was halted in 1999 due to rampant abuse. We could do something like that, but it hasn't worked historically.
Washington State in the Pacific Northest