As a cyclist, I don't avoid sidewalks for pedestrian safety, I avoid them for MY safety - if you're traveling faster than a slow jog, motorists likely will not notice you barreling down the sidewalk towards the driveway/intersection where your paths cross. If a street is too busy for me to deal with the traffic, I might opt for the sidewalk (at pedestrian speed) but will probably find a side street instead. Occsassionally I will use a sidewalk (at pedestrian speed) to travel against traffice, avoid an obstacle in the roadway, or avoid a traffic control at the top of a T intersection. Fortunately for me, my city has recently removed all sidewalk riding bans where the prohibition is not explicitly posted (and now requires that there be a "low stress" bikeway available before they can post the signs).