It would be a failure. Turns out they do something stupid. People tested this in sf by calling a bunch of waymos at once for a prank, but I guess that is the best case example of what a panicked evacuation on the service might be like. It was like a ddos attack. They ended up gridlocking themselves and turned it into a real life version of one of those rush hour board games. No one got out of the little area they called the waymos in.