- Autonomous cars will massively reduce income from speeding fines
- Electric cars will reduce the incoming tax revenue from buying fuel (in Australia this is a large component that also goes into funding the maintenance of the roads)
- Solar power reducing overall household spend on power, which is potentially another large source of tax revenue
The last two things keeps more money in the pockets of consumers, which will therefore probably get spent on other things, so could be closer to a zero-sum game than it looks.
Until some kind of rule change comes in to create new government revenue streams, it's the early adopters getting the benefits so far (for example, Australia is considering additional taxes on electric cars to make up for the 'road maintenance' component the government won't be getting due to their not buying fuel. No word on incentives for "clean air" or "reduced emissions" benefits though...).
They could also use some sort of algorithm that looks at each driver's record. If you have a history of speeding, they can just go ahead and asses extra fees for you since the algorithm extrapolated you would have had more tickets anyways. If you have a clean record, then the algo will go ahead and decide you're "due" for a ticket, and charge you accordingly. Why not, insurance companies do it.
Some people will refuse to buy them for years. People will be buying cheap used cards for years, and those will be normal cars for quite a long time. Dollars to doughnuts the sensors and cameras and whatnot on a lot of autonomous cars will fail before the car itself does, rendering them back to manual. And again the used car market isn't going away.
There might be plenty of manual drivers in fifty years.
I don't think self driving cars will even have a steering wheel. It would probably be cheaper to buy a new car than to convert a self driving car back to manual operation.
The State of Montana had this until the late 1990's, when the Fed's finally forced Montana into having a speed limit again by threatening to pull all Federal highway funding.
Other fun facts are that you could get a driving license at 14 years old (or a "ranch driving license" at 12 in some semi-rare cases), there was no seatbelt law, no motorcycle helmet law, and no law against drinking and driving[0].
[0] There was a law against being drunk while driving, but not a law against drinking while driving. This lead to the classic canard: "How far is it from Butte to Helena?" "Oh about four beers."
Most policing is subjective.
