Never. What are on the road now are dangerous toys that have killed two people and been tossed out of California.
Automation of systems that complex is vastly more important than the public realizes, and even the people trying to design them get rebuffed. The automated baggage system at the Denver Airport, after a $660 million investment, never worked... and it is many orders of magnitude simpler than self-driving cars on public roads. I have spent a lifetime in high tech; maintaining and repairing computer controlled equipment for more than 40 years (46 years if you include analog computers). For the last six years I have been deeply involved in automation of the electric distribution system in our town and it is mostly working as designed... but self-driving cars will be a much tougher nut to crack.
To meet basic design standards they will need redundant sensors and actuators and 2-out-of-3 control computers, just as advanced aircraft do. Similarly, they will have to be designed to exacting standards, ISO compliant, and will have to be serviced, including periodic inspections, by certified technicians. As in aircraft, parts will have to come from certified sources. It is hard to imagine such a thing being sold below $100,000 in today's money or being maintained for under $10,000 per year. Those would be very lowball estimates. A limousine and driver would be cheaper. For that matter, we have no idea how insurance would work. Are those who direct a driverless car to where they want to go responsible if the machine they don't control mows down a crowd of schoolchildren?
The real killer is almost nobody wants one at any price. See the responses to my two questions about them in the sources. They are right, you know... it is essentially the world's most expensive taxi.
Self-driving cars are a delusion - fortunately.