Parking lots shall be provided at the side or to the rear of nonresidential buildings that are visible from public roads; provided, however, that when such placement is not desirable or practicable (in terms of such factors as topography, visibility, aesthetics, shape of parcel, etc.) the off-street parking may be provided between the front of the building and the right-of-way; in such cases, the parking area shall be set back not less than 10 feet, and the setback area shall be developed to form a buffer, as follows: a thickly vegetated buffer shall be provided, and the width, length and planting materials shall be sufficient to visually screen the view of parked vehicles from the public right-of-way.