When stop signs are erected at or near any entrance to Orchard Street and to Hillside Avenue from the Antioch Shopping Plaza, every operator of a vehicle shall stop such vehicle at such sign or at a clearly marked stop line before entering the roadway except when directed to proceed by a police officer, yielding 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 street. (1976 Code § 77.002)