>If you are confused, or your attention is diverted, SLOW DOWN. I say this as a non-commercial driver who has logged $WAY_TOO_GODDAMN_MANY miles behind the wheel.
Driving too fast isn't really a problem in traffic in downtown SF. You're not going to break the speed limit because there's CARS EVERYWHERE.
What the problem is (having lived there for four years) is the hideously bad road signage. You're expected to be able to read two paragraphs of text on a sign within two seconds, to try to figure the fuck out if you're even allowed to be where you are, since the rules change as often as Calvinball. "No left turns except on Mondays through Fridays 7AM to 9AM and 4PM to 6PM". Sign below that: "Except on holidays." Sign below that: "Except MUNI and busses" Sign below that: "Except taxis" is an example of the kind of idiotic sign they expect drivers to be able to read and process while still avoiding pedestrians sporadically jumping into the street.
You also sometimes end up on a Muni line, and you don't know if you're supposed to be there. The answer? Sometimes. Sometimes not.
Then you have the irrational geometry of the city streets themselves, leading to super awesome signs like this:
I once got a ticket from a sign that had six negative modifiers on it, and got it overturned because the bloody cop didn't work through the logic on it correctly and I did.