Those intersections designated on the official map are declared to be stop intersections when entered from the streets first named.  When stop signs are placed, erected,  or  installed at the intersections, every driver of a vehicle or streetcar shall stop in obedience to the signs before entering the intersections 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, § 11-36)  Penalty, see § 70.99