Many of the ideas suggested are good ones but one problem persists. I walk with a friend regularly side by side. Unfortunately, there is not a block in Palo Alto where bushes and branches do not grow over the sidewalk preventing two people from walking side by side.
An effort needs to be made to clear sidewalks and cut back low overhanging branches. Homeowners seem to be oblivious to the fact that the sidewalk belong to Palo Alto and not to them. Please cut back your overhanging branches and sprawling bushes.