> "person getting closer to vehicle" should hold sway for most situations?!?
I think the big thing is that not all of these 'persons' move in the same way. A person in the exact same location could both be a 'hazard' and 'not a hazard' based solely on their velocity, and their ability to change direction quickly (and are they chasing after something which isn't a hazard, but which is intercepting your driving path). They don't just have to identify the person, they have to be capable of forecasting that person's movement.
IOW, someone walking and someone on a skateboard are different risks, because the skateboard could move into your path of travel before your pass them, whereas someone walking would not.