How would you collect a mileage-based tax? Collecting it on the spot on toll roads seems like the most straightforward way to implement it.

Here in Japan the majority of the highway system has been privatized and they all have tolls, and it seems to work just fine. Driving solo between two cities 4 hours away is often more expensive in tolls alone than taking the bullet train.

It would become part of the same process of renewing your registration and getting smog checks. It would probably be like smog checks where there are many depots to get read, run by small businesses and gas stations. I would actually just roll it into the entire smog check system we have currently.

Far more efficient than toll roads, where you have to build toll infrastructure, hire employees, do enforcement and create traffic jams at every toll booth. RFID toll trackers are not enough in preventing the traffic jams. On top of that, you don't have to build anything to implement it today to create a usage tax for roads, since smog check equipment already checks your mileage. It also applies to all roads instead of a select few roads. To determine the distribution of where the tax money should go, you use the passive traffic tracker systems we have almost everywhere.