Ha. Though my guess is, once self-driving is reliable enough to do that, the economics of car ownership are going to flip completely. It won't make sense anymore to have a car that spends most of its time sitting unused in your garage.
Imagine then making those vehicles larger to enable not only a decrease in traffic, but an increase in housing density, local infrastructure in walking distance, and economic growth.
Imagine if we then realized we could charge that elongated car as it's driving if we put electric lines above streets.
Oh, and why not increase rolling efficiency while we're at that, and make the task of self-driving simpler by embedding signaling infrastructure into the road itself.
You just imagined buses, trolley buses, and streetcars respectively.
Which is what makes the most sense, and will continue making the most sense for vehicles that don't sit in your garage most of the time.
There's more to car ownership than being able to get from A to B in principle.
Once you add immediate availability, individual vehicle preferences, having your stuff in the car already, the ability to keep your stuff there once you arrive at your destination, never having to think about small, but normal usage damage (especially if you have kids), or, conversely, having the vehicle just as clean as you want it...
...you will see that garages aren't going anywhere any time soon, self-driving cars or not.
And that we'd be wise to develop actual public transport infrastructure for the people who really do only care about getting from A to B, with some acceptable wait time. It's a win-win for everyone.
My pessimistic prognosis is that the development of the self-driving car will make the taxis slightly cheaper, but instead of paying your Uber driver, you're going to be paying engineers, maintenance, and cleaning staff.
Because it was basically 100 years ago when the car industry sought to dismantle that infrastructure, and succeeded.
That is to say, there's enough there to suggest that this wasn't the free market answering solely to consumer demand.
If you follow the same 100 year trajectory in other countries, then you will see an uptick in car ownership for sure, and infrastructure adapts to support this (highways/freeways/motorways), but it's not nearly as drastic as it is stateside.
Of course, the US is a large place and even its states are larger than other countries. And it hasn't existed in its modern form for more than a couple of centuries whereas the civil infra on the other continents has been around for at least a full millennium and most likely longer than that (e.g. Roman roads in the UK that would date back well over 1000 years). So the US got the luxury of a blank slate and, well... see what you got from that.
At the same time...car manufacturers had the perfect opportunity to seize so they could sell more cars and thus have civil infrastructure designed around the fact that everyone has a car. If someone at that point in time had more money than Henry Ford they could have dumped it into trams and trains and the landscape would have been significantly changed.
As the Wikipedia article you cited elsewhere discusses, streetcar systems outside the US went out of business at the same time as those in the US for the same reasons.
[1] No, kids, Who Framed Roger Rabbit? isn't real history
When there's funding for highways but not rails, the results are unsurprising. The benefits of public transit are a positive externality[1][2].
[1]https://en.wikipedia.org/wiki/Externality#Positive
[2]Real history is way worse
There's no public transport in the US, aside from a few exceptional places like NYC, Seattle, Boston (maybe), and, like, DC.
Uber is so popular because it actually allows you to get from A to B, for some money.
But I love the circular logic of "nobody wants the buses, why fund them" — "you can't get anywhere on a bus, why fund them" — "look how few people ride the bus" etc.
I could rent every single one of these, but don't because the economics don't make sense, and the use model would otherwise lead to a lot of inconvenience.
Except it didn't work for ZipCar or the rental agencies that have added hourly options -- sure it's not bad, but is it really pushing people out of car ownership? No...
Ride sharing similarly hasn't worked to push people out of car ownership either -- it's just killed traditional taxi services by compensating drivers less and eliminating the flag down monopoly some cities have maintained (a taxi medallion in Boston/NYC used to be worth hundreds of thousands... no one wants them now)
All these share options work for low use scenarios like the city dweller who wants a weekly trip to a shopping center, but for the daily commuter/driver it won't ever make sense... and it'll never make sense for those that need to keep things in their car like child seats, diapers, a walker, tools, etc...
Bike/Scooter shares haven't eliminated personal ownership either because of the scarcity issue at peak times.
Have these people never been in the back of a taxi, or any kind of public transit?
In the early days, it was great. But once membership increased, there was an increasing chance that I would get a car that was not particularly usable.
Filthy on the outside (dirt, mud, etc) and/or inside (dog hair, bodily fluids, etc).
Or a car that had one or more warning lights illuminated (check engine, brake, no wiper fluid, low gas, etc).
And each time I had to phone into Zipcar support to report it (and/or swap cars), otherwise the next user could report it -- leading to me being charged some cleaning fee or such.
The best experience I had was in Seattle when I entered a dirty Zipcar and called support who said I had to take the vehicle to a car wash otherwise they would charge me a cleaning fee.
While I understand I could have probably escalated to someone who understood the situation ("oh? you just got into the car 5 minutes ago?"), I decided it was a better use of my time to avoid short-term car rental programs altogether.
Less hassle with verifying who actually trashed it, but also if you have to stare someone in the face after your ride, you'll probably be more respectful of the car.
But really, there's just not a satisfactory solution I can think of to make me want to use the service.
A couple I know in SF don't have a car but they seem to make a lot of use of cars in some form or other pretty regularly.
Presumably if the rate of mess is low enough and there are extra cars, you would just request a new one. Then they punish the person who left the mess or odor, disincentivizing them from doing it again. Probably need cameras monitoring the inside of the car.
While I honestly don't expect door to door self driving in most places for decades, a lot of people who don't use cars much probably underestimate the degree to which many people customize their vehicles. And even if they sit a lot of the time, most of the cost is often in miles, not time.