For your intents and purposes, how is a runner different from a slow cyclist? Just treat him as such. Real simple.
Funny, how cyclists get all offended (rightly so) when drivers insist that they get off the road and/or use a door zone bike lane or a shoulder full of debris and potholes. Yet when a runner chooses not to use the sidewalk (presumably because it is dangerous and/or inconvenient to him, same way a bad bike lane is for a cyclist), the Bike Forum folks suggest the very forms of aggression they encounter from motorists. How ironic. (No, I don't run, and I don't have any connection to any running community.)