(a) about to enter or cross the roadway of a through highway shall yield the right-of-way to any pedestrian legally crossing the roadway and to any vehicle approaching so closely on the through highway as to constitute an immediate hazard,

(b) about to enter or cross the roadway of a highway from a private road or driveway, or about to enter a private road or driveway from a highway shall yield the right-of-way to any pedestrian as may be necessary to avoid a collision and any vehicle approaching so closely on the highway as to constitute an immediate hazard.