Most humans aren't particularly good drivers. Even with an occasional failure, I'd bet driverless tech reduces fatal and non-fatal accidents substantially.
Oh, believe me, I'm poignantly aware of the fact that too many human drivers are very ill-suited for the task of not killing pedestrians, bicyclists, other drivers and babies in baby carriages. I figured this into my response! The problem with these human drivers is that they seem to think they are asleep and dreaming (many actually are), or that they are playing some kind of video game (again, man of them are). What they lack is attention, which is diverted at a moment's notice by any shiny thing (or thought, memory.... I get that! Many drivers don't even know what they are doing is putting everyone around them at risk. They are, in short, really dumb. Don't give them firearms!
My point is not relevant to all of this. My point is that the technology does not exist at present to have driverless cars that will not on some occasions do just as poorly as a poor human driver, or even much worse. Which brings us to ...
But at this stage of the game, one big failure might be enough to put it on hold for years.
There will not be one big failure as long as the roads, streets and highways of our society are the test site for this failed and inadequate technology. There will be just enough failures to insure that the public relations catastrophe will inevitably come, again and again and again. The reason is simple: Machines are
terrible drivers in real world complexity (actual driving conditions). Nothing can done to change this fact ... until these damned contraptions can ubiquitously pass the Turing Test, passing as humans. Even if that were to occur, the cost per unit would be prohibitive in your lifetime, my lifetime and the lifetimes of our grandchildren (where applicable). Let's leave the more philosophical questions to those grandchildren to contend with. We, on the other hand, should know better.