https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...
There are 2 stats that could prove meaningful for this: some average of distance driven between human interventions, and percentage of driving conditions covered. Then compare this to human stats, I'd assume the average human driver might go 10000Km without incident while covering 90% of driving conditions (like everything except extreme weather or road conditions). A self driving car would have to match that.
In other words AP only has 5 deaths because those were the only drivers who left it unsupervised. I'd guess that if every car in the world today would suddenly be driven by a computer we'd see worse numbers than with human drivers one way or another (efficiency, deaths, etc.). Self driving today is great as an assist, with the human still fully in control.
Human miles include all conditions/situations. Autopilot disengages whenever it is convenient and human handles all harder situations.
How about comparing same type of miles?