No person other than an officer of the police department or members of the fire department or a person authorized by the chief of police or a person authorized by law shall direct or attempt to direct traffic by voice, hand or other signal, except that persons may operate, when and as provided in this title, any mechanical pushbutton signal erected by order of the public works director or their designee(s). (Ord. 1628 § 4, 2016: prior code § 3202.1)