There's also the issue of technical problems with for example traffic lights. I remember an occasion in Berlin where the traffic lights broke down on a major intersection with long queues. The right of way ended up being solved in a contest between the status quo competed with the impatience of those who were waiting. The only way as a pedestrian to get across was to step out into the street so cars would stop, which was a bit uncomfortable. Worked out alright, if not terribly efficient. Fixed pretty fast, I think, but an AI would still have to handle, uh, dynamic traffic in western countries.

Ideally, the AI should be able to figure out how the dynamics of such a situation work and not create a jam or something.