If federal law permits the operation of passenger buses wider than 96 inches on the interstate highway system, the Commissioner of Highways may permit the operation of passenger buses of a total outside width, excluding the mirror required by § 46.2-1082, of more than 96 inches, but not exceeding more than 102 inches, on interstate and defense highways or any other four lane divided highways under the jurisdiction of the Commonwealth Transportation Board. The use of any other state highways between the aforesaid highways and the passenger bus terminals may be permitted upon application to the Commissioner of Highways by the governing body of any county, city, or town in which such other highways are located. Any such increase in width of passenger buses or designation of highways to be used by them shall not exceed the federal law which may hereafter be adopted, or jeopardize the Commonwealth’s allotment of or qualification for federal aid highway funds.