that doesn't make any sense though - self driving is a capability, not a type of car. it would be like taxing cars that have cruise control. fundamentally self driving is a safety feature, why would you tax it?
Tolls in cities for traffic control are common where needed. It works well and is simple.
You could tax owning a car more or putting the car in traffic in general, not necessarily self driving aspect of it. The main tax being about taking up room in the streets.