Whenever any ordinance designates and de scribes a through street, there shall be a stop sign on each and every street intersecting the through street or intersecting that portion described and designated as by any ordinance unless traffic at any intersection is controlled at all times by traffic-control signals; provided, however, that at the intersection of two through streets or at the intersection of a through street and a heavy traffic street not so designated, stop signs shall be erected by the approaches of either of the streets.
('76 Code, § 7-1081)