Right now autonomous cars get confused by a pedestrian waving them through an intersection, so it seems to be a ways off before cars can count how many kids are on a bus and then making a decision on it. And when most cars are autonomous, most of these types of accidents will be avoided by the cars communicating and making avoidance maneuvers ahead of time, like you said. But BEFORE most cars are autonomous, this dilemma will probably be more pronounced. I don't see how a driver (is he a passenger at this point?) can make a last second override to change the car's decision, so programmers are going to have to consider this. Given the option, virtually everyone will choose to save themselves if the car can be put in "Save Me First" mode, but that would come with some ethical ramifications. I'm going to wait and see what people who think about this stuff all day long have to say about it. Some day.