Where such parking or storage in residential areas adjoins a more restrictive residential district, they must be separated by a solid masonry wall six feet in height. The solid masonry wall, however, cannot exceed 42 inches in height where it is in the front yard area of an abutting residential use or district. For parking, storage or display in a commercial or industrial area or serving a more intensive use such as a school, adjoining any residential zone or use, it must be separated therefrom by a solid masonry wall six feet in height or up to a maximum height of eight feet with approval of the Planning Commission, provided the wall does not exceed 42 inches in height where it abuts the front yard of a residential use or district. Where such parking area abuts a street in a residential district, it must be separated therefrom by a solid ornamental masonry wall or fence, or compact eugenia or other evergreen hedge or combination thereof, having a height of not less than two feet and maintained at a height of not more than three and one-half (3-1/2)feet. Such fence wall or hedge must be maintained in good condition at all times. Where no fence or wall is required along the boundary of an area covered by this section, there must be a concrete curb not less than four inches by four inches in cross-section securely installed and maintained as a tire stop and safeguard to abutting property or public right-of-way. The barrier must be not less than two feet from any property line or public right-of-way.