The driver of a vehicle shall stop in obedience to a stop sign at an intersection where a stop sign is erected pursuant to ordinance at one or more entrances thereto and shall proceed cautiously, yielding to the vehicles not so obliged to stop which are within the intersection or approaching so close as to constitute an immediate hazard, unless traffic at such intersection is controlled by a police officer on duty, in which event, the directions of the police officer shall be complied with. See Schedule "A" for designated stop intersections. (See 625 ILCS Sec. 5/11-302)