Mo. Rev. Stat. § 300.285

The driver of a vehicle within a business or residence district emerging from an alley, driveway or building shall stop such vehicle immediately prior to driving onto a sidewalk or onto the sidewalk area extending across any alleyway or driveway, and shall yield the right-of-way to any pedestrian as may be necessary to avoid collision, and upon entering the roadway shall yield the right-of-way to all vehicles approaching on said roadway.