A self-driving car approaches an intersection. The light turns yellow. Another vehicle trails closely behind.
Should the self-driving car speed through the intersection? Hit the brakes? What if the tailgating vehicle is 30 feet behind the autonomous one instead of 20 feet? What if the roads are wet? What if there are pedestrians near the road?
Speed, distance, road conditions. The number of permutations from a single general scenario are almost endless.