I think the dominant issue with autonomous cars (bearing in mind, I consulted on a few pushes in that direction) is going to be liability.
Currently, a driver is held responsible, and as such, has insurance. Let's say your liability portion is on average $500 per year. Well, assuming 100 million licensed drivers, that's $50 billion. Given that the profit margins aren't all that huge, let's assume the insurance companies pay out probably 50% of that in a given year.
The issue is when its no-longer an individual responsibility. When an autonomous car crashes and kills someone, who gets the bill/lawsuit. If its the individual, then all is well. But it seems like a good market for trial attorneys. If its the mfg, then their insurance isn't really insurance, its cost of doing business, to the tune of potentially billions right off on the bottom line, a cost factor that I don't believe had been adequately folded in.
And WHEN (not if) an error is discovered, the punitive damages are going to be insane.