The city council may designate by resolution such intersection where no vehicle shall be turned at any time in a complete circle or in a manner as to proceed in the opposite direction upon which the vehicle is traveling at the time of entering the intersection.  The city engineer shall place and maintain signs giving notice thereof at all intersections so designated and no such regulation shall be effective unless such signs are in place.  (Ord. 486 § 4 (part), 1992:  prior code § 13-5.3)