You would either have to add massive taxes to road usage (not just gas), heavily tax automobile ownership or use general purpose taxes for such very expensive upgrades.
As a non-owner of a car I would balk at the last option.
You're assuming the upgrades will be extraordinarily expensive. What if what is required is something as simple as radar-reflecting paint, and somehow encoding additional information in the markings? Or maybe all cars should have an RFID-like thing on their bumpers to make car detection more reliable. The gov't could distribute that bumper sticker along with the car registration sticker. You could enforce that in the annual inspection.
Sure, a car that doesn't need any aids is much cooler. But if you look at the history of technology, especially in the PC world, there were a lot of clever hacks and external aids that had to be used in order to make the tech feasible. Then with time, they were rendered unnecessary.
You would either have to add massive taxes to road usage (not just gas), heavily tax automobile ownership or use general purpose taxes for such very expensive upgrades.
As a non-owner of a car I would balk at the last option.