(A)   Those streets and parts of streets designated on the official map are declared to be through streets for the purpose of this section.
   (B)   When stop signs are placed, erected, or installed upon highways intersecting a through street at the entrance thereto or at the entrance to any intersection, every driver of a vehicle shall stop in obedience to the signs before entering the intersection and shall not proceed into or across the through street until he has first determined that no conflict with traffic will be involved.
('72 Code, § 11-35)  Penalty, see § 70.99