No person shall park a motor vehicle or leave a motor vehicle standing unattended except on an improved surface as defined in Chapter 1242 of the Zoning Code. This restriction shall not apply to those portions of industrial land or municipally owned land that is not part of a required parking lot or loading zone and that is effectively screened from view of any adjoining property. Temporary parking (not to exceed five consecutive days) in athletic fields for special events will be allowed by order of the Safety/Service Director.