The operator of a bicycle emerging from an alley, driveway, or building shall, upon approaching a sidewalk or the sidewalk area extending across such alley, driveway, or building exit, yield the right-of-way to all pedestrians approaching on said sidewalk or sidewalk area, and upon entering the roadway shall yield the right-of-way to all vehicles approaching on said roadway. (Code 1962, § 37-25.02)