Two facts:
- The average occupancy of a car in my North American city is 1.2 people per car. This does not vary much by city.
- Autonomous vehicles will almost certainly be worse for traffic than human driven cars. They will circle empty with no passengers and drive to pick up passengers empty (dead heading) even with a fully rideshare system. If there is widespread private ownership of autonomous vehicles (and you bet your butt that car companies will campaign for this aggressively to keep sales up), the dead heading problems only multiply. If you don't believe me, look up any recent literature on the topic: by most accounts it will be worse, not better. Dead heading is only the tip of the iceberg of problems there.
The downvotes on this comment are a testament to the privilege of drivers. It's crazy how good people, who would otherwise not break the law, believe it's their right to speed. And before someone tells me it's a victimless crime I'll remind everyone that speeding kills both those inside and outside of your car.