There's more to it than that. Traffic is as safe as it is (I won't call it flat-out "safe"), in no small part because people can anticipate other drivers. A _predictable_ driver is a safe driver. Having self-driving cars randomly stop short is a quick way to rack up a lot of "not legally at fault", but perhaps morally at-fault, accidents.

FWIW, if you've ever done car/bike track days, this is a huge reason why it's so safe. People are split into groups according to skill level, with restrictions on passing (normally "only on the straights") for the lower groups. Much of the "skill level" here is actually just being predictable, not being outright fast. Someone can be in a Miata getting passed with a 50mph speed differential on a straight _because everyone is being predictable_. That same Miata might pass the same car with a huge speed differential at 90 mph in a turn, and it works because everyone is predictable.