Those streets and parts of streets described in Schedule I on file in the office of the City Clerk are hereby declared to be through streets for the purpose of this section.
Whenever any ordinance of this City designates and describes a through street, it shall be the duty of the Director of Public Works or his/her designee to place and maintain a stop sign or, on the basis of an engineering and traffic investigation at any intersection, a yield sign on each and every street intersecting such through street unless traffic at any such intersection is 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 said streets as may be determined by the Director of Public Works or his/her designee upon the basis of an engineering and traffic study.