Well, in the small sample size we have to work with, it appears Google’s cars are involved in accidents at a rate triple the national average, so the data’s already not promising.
That said, the problem I’ve always had with driverless cars is “Captaincy.” Simply put, if you want to “take over” for the driver, you have to take over ALL driving aspects, which includes more than manipulating the controls. You need sufficient Situational Awareness to make valid “go/no go”; “continue/no continue” decisions. I don’t see a driverless car doing that well, or at all.
For example, I once had to drive from Pitsburgh PA to Albuquerque NM just after the Christmas holiday. Unfortunately, there was a horrible winter storm scheduled to blow through. It was big enough that the precipitation would essentially span the US from northern to southern border, and was supposed to pick up over a foot of snow.
Knowing this (SA), I made the decision NOT to take I-70 to I-44 through St Loius, and cut down to I-40; I decided to cut south through the Appalachians, ahead of the storm, and pick up I-40 in Nashville, before the weather made it that far east; that way, I’d be above the freezing point (hopefully), and have rain–not snow or ice–to contend with.
As I travelled, I kept an eye on my ETA, and kept the radio on to measure the progress of the storm. I had a bit of a scare when I began to encounter freezing rain; fortunately, a two-hour dinner ensured that the temerautre was back above freezing when I continued. Good thing I detoured–St. Louis got something like 2’ of snow!
I don’t see a “driverless” car doing that well, or at all.