Just about every outcome of this would be good. It would reduce miles traveled, give the chance to charge people for the damage they do to the road, and encourage more compact development patterns. We know by the way people choose to use or forgo toll roads that drivers place very little value on their time compared to small amounts of money, so they'd theoretically be very responsive to per mile charges. We'd then get more direct feedback that would hopefully demonstrate where actual demand, rather than extrapolated theoretical future demand, exists. The funds could go back to the places where the driving and consequent road damage occurred, too.

But I don't know how you implement this in such a low-trust environment, since it amounts to everyone's vehicles being tracked. I guess you could just make all the data move like credit card bills (e.g. data transmits weekly, so my upload for this coming Monday covers from 2 Mondays ago to last Monday.) That would prevent government entities and, in turn, everyone who has compromised those government systems, from having real time dragnet tracking.

Then there's massive incentive to cheat on the part of drivers, so you need this system to be perfectly secure despite the device being in the hands of the the would-be cheaters. Then, what happens if the device breaks, failing to report the data?

*Edited to clarify what's good about it.