(a) Preferential right of way may be indicated by stop signs or yield signs as authorized in Code Section 32-6-50.

(b) Except when directed to proceed by a police officer, every driver of a vehicle approaching a stop sign shall stop at a clearly marked stop line or, if there is no stop line, before entering the crosswalk on the near side of the intersection or, if there is no crosswalk, at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway before entering it. After stopping, the driver shall yield the right of way to any vehicle in the intersection or approaching on another roadway so closely as to constitute an immediate hazard during the time when such driver is moving across or within the intersection or junction of roadways.

(c) The driver of a vehicle approaching a yield sign shall, in obedience to such sign, slow down to a speed reasonable for the existing conditions and, if required for safety to stop, shall stop at a clearly marked stop line or, if there is no stop line, before entering the crosswalk on the near side of the intersection or, if there is no crosswalk, at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway before entering it. After slowing or stopping, the driver shall yield the right of way to any vehicle in the intersection or approaching on another roadway so closely as to constitute an immediate hazard during the time such driver is moving across or within the intersection or junction of roadways. If such a driver is involved in a collision with a vehicle in the intersection after driving past a yield sign without stopping, such collision shall be deemed prima-facie evidence of his failure to yield the right of way.