It blocks a single road and yet that makes the news and people have to route around it and it disrupts a day.
What happens when one company's engineering failure does that to most roads?
For reference, the US considers tactically blocking traffic to be something that smart terrorists or nation state adversaries would want to do to significantly harm the US economically.
What do these cars do if Google's entire self driving infrastructure falls over because some component gets misconfigured? It will happen eventually.
That's hardly new. What do you think happens to traffic when a semi flips over on a busy interstate, or electricity goes out, turning all traffic lights into 4 way stops and severely limiting throughput?