An analogy for self-driving cars

This is Joseph

I see this sentiment a lot with self-driving cars:

Many industry observers, yours truly included, believe autonomous vehicles have the potential to be far more disruptive than EVs, because they upend the logic of automobile ownership. Most cars sit idle at least 20 hours a day, which is incredible wasteful. But if you could simply summon a private, robot car at will, utilization would increase. This, in turn, has the potential to make mobility much cheaper — it’s public transportation on steroids!

I am not going to say that this idea is wrong.   But let's consider something else that is idle 20 hours per day, has both public and private versions, and there could be efficiencies in reducing duplication of facilities.  I speak of the restroom.

It is immediately obvious that we could make plumbing a lot more efficient if we had a public restroom building on each block and no restrooms in houses.  Or shared restrooms for hotels and apartments.  Restrooms spend a lot of time empty and we could make houses smaller/cheaper if we did not include them.

Why don't we do this?

1. Queuing -- people often want to use the shower or toilet at similar times of the day (say the morning before work)
2. Convenience -- even if the walk is short, it's shorter to have the toilet inside your own house
3. Upkeep -- who is responsible for cleaning and repairing the facilities, especially at 2 am when somebody gets sick
4. Privacy -- people like private spaces
5. Customization -- maybe you want a handicapped shower or a bigger mirror

This doesn't mean we don't have public restrooms.  We do.  But we are also in no danger of replacing the personally owned restroom with the public version.  And I think a lot of the same objection apply to this transition.  

Now this is an analogy -- it's not exact.  But I think we can immediately see that there are reasons that the robot car model might have issues with implementation.  Now, this doesn't mean people won't own their own robot cars -- they sure will.  But the public transportation fleet of robot cars is going to either be a company or the government (today's options).  

So maybe this innovation will happen.  But it would be most successful among income constrained urban dwellers.  These are also people most likely to share other things.  But the road to instantly summoned robot cars is not absolutely clear without a lot more coordination than I expect to see.