I have to confess my road manners have been really going downhill lately. I think it’s a gradual reaction to poor drivers that I’ve gradually become a poor bicyclist. As far as the road/sidewalk comparison, I think the relative rate of speed needs to be taken into account. Cars and bikes are often traveling at the same rate and therefore are more predictable to each other. Bikes and pedestrians are usually traveling at very different rates and a reduce the reaction time for both.