The city engineer is authorized to determine those intersections at which operators of vehicles shall not make a right, left or U-turn, and shall place proper signs at such intersections. The making of such turns may be prohibited between certain hours of any day and permitted at other hours, in which event the same shall be plainly indicated on the signs, or such signs may be removed when such turns are permitted. (Ord. 5212 § 1 (Exh. E), 1999; 1957 code § 9.04.200.)