The Police Chief is hereby authorized to establish temporary parking restrictions on all streets, alleys, and City-owned parking lots for special events, construction projects, and at other times as said official deems necessary. The Police Chief shall erect or cause to be erected appropriate signs giving notice thereof, and no such temporary restriction shall be effective unless signs are erected and in place at the time of the alleged offense. When the signs are so erected, giving notice of the temporary parking restrictions, no person shall disobey the restrictions states on such signs.