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