Introduction
Self-driving cars are not allowed in the public road and street network without human supervision anywhere as far as I know but the time will eventually come when they will be. For example, part of Tesla's value proposition is to enable the owners of future Teslas to make money on their vehicles as they are available for use all the time except for when the owner needs them.
The cost of car ownership is pretty substantial
Here's a link to a car ownership cost calculator that you can play with:
https://financialmentor.com/calculator/car-cost-calculator
The default example is a $25,000 car financed with a 60-month plan, a $1000 down payment, a 7.9% financing rate (APR) and a three-year time of use.
At an annual driving mileage of 20,000, the cost comes down to $0.56 per mile.
That's nothing to scoff at, in other words expensive AF.
Would autonomous vehicles be cheaper as a service?
These are the taxi rates in New York City:
https://www.taxi-calculator.com/taxi-rate-new-york-city/259
The kilometer price is the same per night. It's $2.5 per mile.
The question is how much of that is the share of the driver.
I found this article:
http://urbankchoze.blogspot.com/2014/08/what-taxis-can-tell-us-about-driverless.html
Where there was a breakdown of the cost structure for running a taxi service for two different years in Canada.
The driver's income accounts for about a half of the cost of the operating costs of a taxi service.
More uncertainty would be introduced by the cost of all the equipment and software costs baked into the operating and purchasing price of an autonomous vehicle. But we can assume that these costs will come down rapidly because they're IT.
Also, a driverless taxi has one more seat available to passengers.
But assuming that a driverless taxi ride would cost half as much per mile, the cost per mile would still be about $1.25 per mile.
Conclusion
If you drive a lot, owning a car would still make sense in a world where driverless cars are both allowed to drive without human supervision and where the tech is inexpensive. But if you drive much less than 60 miles a day on average do not drive regularly, car as a service will make more sense than it does now because the cost could potentially be roughly a half of a regular taxi.