Any county may expend so much of its general revenues as its governing body by majority vote of its elected members deems appropriate for the construction and repair of public roads not in the primary or secondary state highway system and may own and operate the properties and equipment necessary to carry out the provisions of this section. Any county revenues expended for such roads shall not be considered to be highway funds which are made available for highway purposes pursuant to § 33.2-358 and shall not diminish funds paid to counties under § 33.2-358.