The city traffic engineer is authorized to determine those intersections at which drivers 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 they shall be plainly indicated on the signs or they may be removed when such turns are permitted. (Ord. 432 § 2 (part), 1982).