it doesn't need to be invasive or expensive. in my state I need to get an emissions test every few years, which simply consists of plugging into the ODB jack and reading some values. just take an odometer reading while you're checking the emissions data and charge based on the difference since the last reading.
I suppose you could argue that some people do significant driving off of public roads, but that's probably rare enough that special exemptions would be feasible.
all of this sidesteps the real issue, which is that personal vehicles do negligible damage to the road. road wear from commuter traffic is almost negligible compared to large trucks.
It does however lead to a lot more tampering with odometers.
In New Zealand diesel vehicles pay a significant tax per kilometre, and so there are a lot of people disconnecting odometers. There are even people for who their only income is from "rewinding" or reprogramming electronic odo readings (using a variety of techniques, sometimes cracking ECUs etcetera). There is some incentive to reduce recorded milage to enhance resale value, but a lot more incentive to reduce taxes. Edit: I could be a victim of selection bias here because most people will happily admit to ripping off the government while fewer people will admit to ripping of other individuals.
Large commercial vehicles have government mandated secondary odometers, which I haven't heard as much about tampering: maybe because tampering happens less, or maybe because the penalties are higher, or maybe it happens but I am not in the loop. Also the likelyhood of getting caught tampering truck odos is higher because trucks are stopped far more often than cars, and trucks are checked far more carefully.
> just take an odometer reading while you're checking the emissions data and charge based on the difference since the last reading.
An odometer reading won't say anything about where I drove that vehicle. If you take your car offroading or go on road trips a few times a year, that alone will skew the numbers heavily. With that in mind, odometer reading works fine for emission tests, but not so much for road damages. And constant vehicle ___location tracking reported to the government for the purpose of paying annual registration fees sounds pretty invasive to me.
But also, perfect is the enemy of the good. While the solution I proposed is not as comprehensive as the one that includes tracking mileage (and dealing with all the problems and issues associated with it), it is still significantly better than what we have now.
I suppose you could argue that some people do significant driving off of public roads, but that's probably rare enough that special exemptions would be feasible.
all of this sidesteps the real issue, which is that personal vehicles do negligible damage to the road. road wear from commuter traffic is almost negligible compared to large trucks.