No person shall operate a vehicle exceeding a size as specified in Section 339.03 or exceeding a gross weight of five tons, upon any street in the Municipality other than a State route, except those local streets designated as a truck route and marked as such by appropriate traffic signs, and except when such operation is necessary to load or unload property, to go to or from the usual place of storage of such vehicle or to perform any other legitimate business or act other than passage through the Municipality. Operators of vehicles so deviating from either a State route or a designated truck route within the Municipality shall confine such deviation to that required in order to accomplish the purpose of the departure.