Whenever any ordinance of the city designates and describes a through street it shall be the duty of the city traffic engineer to place and maintain a stop sign on each and every street intersecting such through street or intersecting that portion thereof described and designated as such by any ordinance of the city unless traffic at any such intersection controlled at all times by traffic-control signals; provided, however, that at the intersection of two such through streets or at the intersection of a through street and a heavy traffic street not so designated, stop signs shall be erected at the approaches of either of such streets as may be determined by the city traffic engineer upon the basis of and engineering and traffic study. (Ord. 210 § 63, 1957)