"At fault" is one relevant metric, but not the only one. An autonomous vehicle should at least meet, and ideally surpass, human-driven ones in avoiding accidents for which they're not at fault as well.

I'd be curious to know if Waymo vehicles experience more, less, or the same number of not-at-fault accidents per mile driven as human-driven ones.

That's a tricky one. Avoiding an accident for which you are not at fault could easily cause an accident for which you are at fault. Human drivers have a pretty bad record with that particular situation.

Also, there are some network effects at play here, the higher the percentage of self driving cars the more rare that situation should become.

I agree that there's a tricky calculus involved in some scenarios, but I think there's a much wider domain of not-at-fault scenarios where autonomous vehicles should be able to surpass humans unambiguously. Example: an autonomous car being tailgated by a human-driven car, with a stop sign or light up ahead. Different braking patterns have different likelihoods of causing an accident.

Autonomous cars really have to be able to handle these scenarios at least as good as, and ideally better than, humans: there's not a complicated split-second balancing act to worry about.

Tesla have stats saying their autopilot, for all its limitations, is already much safer than a human driver: https://electrek.co/2017/01/19/tesla-crash-rate-autopilot-nh...

Humans will do stupid things. A self-driving car has to drive safely in spite of them.

How do you avoid being rear ended at a stoplight?

There may be ways to avoid some of the other types of accidents, but those ones (which have happened several times) are difficult to escape.

The real question is what's the safety threshold - safer than median human? 90th percentile? 99th?

> "How do you avoid being rear ended at a stoplight?"

The same way defensive (human) drivers have been doing for a long time: leave room between you and the car in front of you. Gauge cars coming up behind you and roll forward if they need extra room to stop.

Does not prevent 100% of rear-endings, but a large portion of them. Most rear-enders are not cars plowing full-speed into you, it's someone misjudging their braking and not being fully at-rest when they needed to be. Leaving some margin for this kind of error helps avoid the whole incident.

Change lanes, allow the other driver to overtake, start braking a little earlier and more gently, touch the brakes to flash brakelights let the driver behind know that you are stopping soon. All ways i deal with tailgaters in different situations - it's a judgement call though.