Except when expressly authorized in writing by the county, the following vehicles are prohibited from entering upon a county-owned and -operated public parking facility:
(1) Any trailer or towed vehicle.
(2) Any truck having a manufacturer's rated carrying capacity greater than (1) ton.
(3) Any vehicle with a gross weight greater than eight thousand (8,000) pounds.
(4) Any vehicle having an overall length more than twenty (20) feet including any load thereon.
(5) Any vehicle wider than eight (8) feet.
(6) Any bus. (1978 L.M.C., ch. 7, § 2.)