Maybe put a bunch of them in a test track area like this one in Concord, California. Gomentum is Silicon Valley's secretive test track for self-driving cars:
https://www.cnet.com/videos/inside-silicon-valleys-secretive...
I do agree that there needs to be a minimum requirement you should reach before being allowed to drive on public roads. Companies should not be alpha testing with human lives.
The test bed should have the 'average moving car density' equivalent to that of an SF/NYC neighborhood.
Let the robots test themselves and risk their 'lives' first before putting real human lives in the mix!
But yeah some sort of random pedestrian/animal/debris in the road testing seems like it will be crucial to prevent this sort of accident from happening again.