All vehicles used in the transportation of any garbage, refuse or other materials of any kind, shall be fully enclosed and shall at all times in transit be kept covered with an adequate cover or canvas cover, tied down in such a manner so as to prevent scattering of the contents of the load. This rule shall apply to all loads of materials likely to scatter in transit. An appropriate cover is not limited to a canvas cover but may be plywood, or some other material, which entirely covers the the load and is securely tied down.