A human would have seen what all the other cars were doing, and emulated that eventually, even if the construction was poorly marked.

It was incredible to watch how Waymo was able to plot the huge number of cars accurately around the vehicle throughout the drive. But as soon as something creative was required, it all fell apart.

I still remember a talk where someone from the original DARPA challenge was recounting an episode where two autonomous cars arrived at an intersection precisely at the same time. They deadlocked because they were waiting for each other to go. A programmer added jitter to work around that situation, but it is one of those things humans innately would figure out.