As far as tech goes, this is mostly a pointless exercise. The car is supposed to know it's in a low-speed urban environment where there may be zebra crossings,

As far as tech goes, this is mostly a pointless exercise. The car is supposed to know it's in a low-speed urban environment where there may be zebra crossings, so it accelerates accordingly and always has time to break. If a pedestrian makes an illegal crossing, the car should try to protect its occupants first, which is the most natural response for a human driver. Not to mention autonomous cars will be more likely to turn these unavoidable accidents into avoidable ones. One can entertain all sorts of situations, but so far I haven't found one without an answer. It always boils down to not including a "split-second morality system".