(a) No person shall place, maintain, or display upon or in view of any highway any unauthorized sign, signal, marking, or device which purports to be or is an imitation of 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 sign or signal, and no person shall place or maintain, nor shall any public authority permit, upon any highway any traffic sign or signal bearing thereon any commercial advertising. This shall not be deemed to prohibit (1) 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, or (2) the temporary placement by auctioneers licensed or exempt from licensing under section 330.01, for a period of not more than eight consecutive hours, on or adjacent to the right-of-way of a highway not more than four signs directing motorists to the location of an auction.

(b) Every such prohibited sign, signal, or marking is hereby declared to be a public nuisance, and the authority having jurisdiction over the highways is hereby empowered to remove the same, or cause it to be removed, without notice.