I believe the evidence strongly suggests that autonomous driving will not only catch up, but greatly exceed human drivers in the foreseeable future. Mechanically, automation is superior to humans for simply operating the car. And the large categories of causes for fatal accidents are low-hanging fruit for automation - lane drift, running red lights, driving too fast for conditions, etc. And sensors can observe the environment as well as or better than eyeballs.

The only real point of contention is in interpreting unexpected hazards, like the infamous bicyclist. But interpreting sensor input is subject to continuous improvement, due to programmer experience, log data, and Moore's Law. So even if that point is weak now, there's no reason to believe it will not improve substantially - in fact, it is unreasonable to believe that it will not improve.

Large categories of potential causes for fatal accidents are things which humans very seldom have issues with but computer programs often struggle with like inferring intent and identifying whether something is animate, which can easily cancel out reductions in other types of accident due to (e.g.) better average lane discipline. Especially when you consider the benchmark for fatalities per billion km driven is around 3.5[1] including fatalities caused by humans considered unfit to drive, and humans who are considerably less experienced and safety-conscious than the likely early adopters of SDVs. SDVs have already had one fatality and several incidents where human intervention prevented accidents in a few million miles of low speed, good condition driving. I think we're a very long way from seeing any indication computers alone will ever beat that benchmark, still less a plausible case that the additional deaths resulting from riskier testing programmes will be cancelled out by lives saved if the first few SDV models go on sale a few months earlier.

[1]a few European countries; it's double that in the US, which also suggests that if you want to reduce road deaths there's a lot of other steps that can be taken which don't involve risky technology experiments.

The alternative is to simply never allow it at all, to assume that humans will always be better drivers than computers. Which opens up an ethical dilemma. If auto-autos could save tens of thousands of lives a year - and it seems at least plausible that it could happen - then to reject it out of hand is to cause tens of thousands of innocent deaths a year.