That doesn't happen with sidewalks because the vast majority of people have at least a tiny bit of politeness and will make way for someone trying to get throug

That doesn't happen with sidewalks because the vast majority of people have at least a tiny bit of politeness and will make way for someone trying to get through. For the extremely rare people who wouldn't, I assume that the police would stop by and get the person to move out of the way, just as they would if people were intentionally obstructing a sidewalk.