> Chances are there were and that they were due to human error.

Eh, I don't know. ~40 people die from traffic collisions each year in San Francisco, so about one every nine days. People would be driving more cautiously without traffic signals or street lights, and most collisions at intersections would occur a relatively low speed assuming drivers treat the dead signal as a stop sign. The risk of death for drivers might be higher during a power outage like that, but I doubt it would be 9x (and the outage lasted less a full day).