So here's a hypothetical scenario. Car drives kids to school (in my experience, school tends to start before work). Drives back empty to pick up parent to drive to work. In the afternoon, car drives (empty) to pick up kids and drive them home, then drives (empty) back to work to pick up the parent. Half the time it's empty.

> Drives back empty to pick up parent to drive to work.

This implies there are no other people for which a rideshare would be suitable in either direction at any given time. This seems, like an unreasonable way to predict how mass AV would work. Again, demand is asymmetrical, which means there are opportunities for aggregation and overlap, when talking about mass adoption to the point that "the majority of cars on the road will have zero occupants".

There's the issue with demand for AV availability (ie traffic), which can never be reduced to zero. This would incentivize better judgement than "I'll stagger the school and work times"

Logically, why would AVs be 1-4 occupant vehicles? Once you have AV, you have AV vans and buses, similar to airport shuttling.

We're not talking about rideshares, we're talking about autonomous personal vehicles. Most people are not likely to give up their personal vehicles; they'll just have self-driving ones.

This seems like an odd argument to me: "enabling efficiency isn't useful if you assume people's habits won't adapt to the new status quo". Once you've moved personal vehicle use of the sort you describe from essential to luxury, I don't see why you couldn't make users bear the cost of their frivolous externalities.

There is no way people would give up owning their own car outside of very dense urban centers. Everywhere else it would neither be practical nor desirable to wait for a rental car to arrive.

People also tend to store lots of personal items in their car.

There are any number of things that seemed utterly critical and timeless to the myopic of their time that are either anachronisms or at best optional today. "There's no ways people will live in apartment buildings", "there's no way people will give up their horses", etc etc

Why do you think people will choose to rent a self driving car instead of owning one?

For the same reason I use a combination of transit, Ubers, and rental cars to get a far better experience than car owners at a fraction of the cost. For the same reason that the average person gave up horses and large plots of land and indoor woodfires for heating and cooking: if something is horribly inefficient and costly relative to an alternative, eventually society stops subsidizing it, and the only ones left doing it are the highly irrational or the highly passionate (compare horse ownership 150 years ago to now).

There are obviously advantages to owning a car that transport-as-a-service doesn't offer, but the point is that once an alternative is available that's better from a global utility perspective, it doesn't make any sense to subsidize the costly decisions of the irrational (barring interest groups that we as a society choose to explicitly subsidize, like families or the disabled).

I don't want to depend on a taxi. I have to drive to work NOW.

Well, obviously. This isn't something you turn off overnight if the alternative infrastructure doesn't yet support it. But you could make the same argument if pretending it's a necessity about any of a million things that don't exist in modern society today. If your definition of what you're entitled to is no different from the status quo, you're barely even coherently engaging with conversations about how society can and should evolve, improve, or maintain its normz and policies.

> We're not talking about rideshares, we're talking about autonomous personal vehicles

> they'll just have self-driving ones.

That won't last long, because of market inefficiency. Why pay for maintenance and energy on a vehicle? It's just as unrealistic as saying we'll keep personal vehicles running on gasoline, to me.

people who can afford it value exclusive ownership of an item. a good example is the vacation home. it's possible to defray the cost of ownership of the second home by a lot if you are willing to rent it out to others while you aren't using it, but most people don't seem to do this. [0]

I suspect that unless it gets banned outright, wealthy people will be happy to pay whatever it costs to guarantee strangers can't leave a bad smell in the vehicle that takes them to work.

[0] only about 30%, according to https://www.washingtonpost.com/business/2018/07/12/study-mor...

In your scenario the number of trips is the same but the car is more often empty because the parent doesn't have to chauffeur the kids around.

Now the parent can be in a different car at the same time, going something else, thus doubling the number of cars on the road.

Yes, that was the point.

But it still takes up space on the road