Every person operating any vehicle shall, upon approaching any stop sign erected in accordance with the resolution prescribed heretofore, cause such vehicle to come to a complete stop before entering or crossing any street, highway, or railroad crossing. The vehicle operator shall stop at a marked stop line, or, if there is no stop line, before entering the crosswalk; but if neither is indicated, then as near the right-of-way line of the intersecting roadway as possible. (Ref. 60-6,119 through 60-6,121, 60-680 RS Neb.)