Subject to RCW 46.61.400(1), and except in those instances where a lower maximum lawful speed is provided by this chapter or otherwise, it is unlawful for the operator of any vehicle to operate the same at a speed in excess of twenty miles per hour when operating any vehicle upon a public highway either inside or outside an incorporated city or town when passing any marked public school or playground crosswalk when such marked crosswalk is fully posted with standard portable school or speed-control signs. The speed zone at the crosswalk shall extend three hundred feet in either direction from the marked crosswalk. (Ord. 407-76 § 1, 1976.)