Barriers. Where parking, loading, or maneuvering areas adjoin a street or streets, a 12 gauge wrought iron fence not less than eight feet in height, a masonry or concrete wall not less than 30 inches in height, or a landscaped area a minimum of four feet in width measured from the property line, or an equivalent protective device as approved by the Director, shall be established along such full frontage, except at driveways, walkways, or other openings where such are necessary. Where a barrier or a landscaped area adjoins a driveway, a 10-inch concrete-filled steel pipe or equivalent protective device shall be installed on driveways used for trucks, and an eight-inch concrete filled steel pipe or equivalent protective device shall be installed on driveways used exclusively by automobiles.