The driver of a vehicle emerging from an alley, driveway, private road or building where there is no official traffic-control device shall stop such vehicle immediately prior to driving onto a sidewalk or onto the sidewalk area extending across any alleyway, driveway or private road and shall yield the right-of-way to any pedestrian as may be necessary to avoid collision, and before entering the roadway shall yield the right-of-way to all vehicles approaching on the roadway.