You may feel it is safe, but it is NOT safe to travel in sidewalks at speeds faster than people walk. You must assume that motorists crossing the sidewalk will only scan far enough to make sure there is no one coming at pedestrian speeds. It is unreasonable to ride at 6, 8 or more MPH across a sidewalk, because motorists are likely to not anticipate anyone doing this. It's very unsafe to ride in crosswalks! This is a common cause of car-bike collisions.

See my longer reply previous for how to properly (and SAFELY) handle intersections like this on a bicycle.

Serge