I doubt that here. Cars are already near saturation, at least in the US.

Essentially everyone has a car. The car is mostly idle. If car availability starts to approach instant then people don't need personal vehicles that are idle 95% of the time. Car quantity overall goes down unless you can 20x current utilization, which is a lot of trips and fuel.

Not to mention that if anything resembling current quantity of extant cars becomes the current quantity of cars using roadways at a given moment, most cities will gridlock.

If the thesis is "cars will approach 50% or greater utilization" then car numbers must drop barring a massive increase in road capacity for which the land does not exist.

Who exactly will be cleaning and sanitizing these self-driving cars that are getting this 50%-or-greater utilization?

> Car quantity overall goes down unless you can 20x current utilization, which is a lot of trips and fuel.

Pretty much every self-driving car will be electric; battery charge has a very different set of considerations than fuel tanks do.

Cars that are idle 95% of the time are replaced less than once in a decade.

Cabs are replaced something like 3x more often than privately owned cars. And when they run 24/7 because of self-driving, that factor will even increase.

> If the thesis is "cars will approach 50% or greater utilization" then car numbers must drop barring a massive increase in road capacity for which the land does not exist.

You can build stacked roads a few levels up. Capacity doubles or triples without any significant land use.