The driver of a vehicle approaching a yield sign erected at those intersections described in appendix I, section 104, shall and in obedience to the sign slow down and yield the right-of-way to any pedestrian crossing the roadway on which he is driving and to any vehicle in movement on the main traveled or through highway or street which is approaching so as to arrive at the intersection at approximately the same time as the vehicle entering the main traveled or through street or highway.