(a) No person shall place, maintain or display upon or in view of any road, street or highway any unauthorized sign, signal, marking or device which purports to be or is an imitation or resembles an official traffic-control device or railroad sign or signal, or which attempts to direct the movement of traffic, or which hides from view or interferes with the effectiveness of any official traffic-control device or any railroad signal or sign, and no person shall place or maintain nor shall any public authority permit upon any highway or street any traffic signal or sign bearing thereon any commercial advertising. This shall not be deemed to prohibit the erection, upon private property adjacent to streets or highways, of signs giving useful directional information and of a type that cannot be mistaken for official signals.
(b) Every such prohibited sign, signal or marking is hereby declared to be a public nuisance and the city is hereby empowered to remove the same or cause them to be removed without notice.