(A)   The driver of a vehicle approaching a yield sign shall, in obedience to the sign, slow down to a speed reasonable for the existing conditions, shall stop if necessary, shall yield the right-of-way to any pedestrian legally crossing the roadway on which he or she is driving and to any vehicle in the intersection or approaching on another highway so closely as to constitute an immediate hazard.  The driver having so yielded may proceed, and the drivers of all other vehicles approaching the intersection shall yield to the vehicle so proceeding.  If the driver is involved in a collision with a pedestrian in a crosswalk or a vehicle in the intersection after driving past a yield sign without stopping, the collision shall be deemed prima facie evidence of his or her failure to yield right-of-way.
   (B)   The driver of a vehicle approaching a yield sign, if required for safety to stop, shall stop before entering the crosswalk on the near side of the intersection or, in the event there is no crosswalk, at a clearly marked stop line, but if none, then at the point nearest the intersecting roadway.
(47 O.S. § 11-403(b))  (`90 Code, § 20-68)