Except as provided in subsections (b) and (c) of this section, a road opened under this subtitle shall be at least 30 feet wide. A road opened under this subtitle is a public road. If the County Commissioners of Somerset County determine that the difficulty or cost of building a road to the width of 30 feet is excessive, the county may build portions of roads that are less than 30 feet wide in: the Smith’s Island district; and the Fairmount district on the road leading from the main county highway to the village of Rumbley. The governing body of Anne Arundel County may take over and maintain as a public road any alley or road in the county that is at least 20 feet wide if the road or alley was open or dedicated for use as a road or alley before June 1, 1943. Subject to subparagraph (ii) of this paragraph, the governing body may take over and maintain as a public road any alley in the county that is at least 10 feet wide and is in a subdivision platted before July 1, 1953. If an alley described in subparagraph (i) of this paragraph does not satisfy the standards and requirements of the State Highway Administration for the purpose of receiving a share of highway user revenues, the expense of taking over and maintaining the alley shall be paid by a special tax imposed on the property owners in the affected subdivision.