Transition Requirements. There shall be established along the line of any lot that is contiguous to any residential district, unless the side or rear lot line coincides with a State or Federal highway or railroad right-of-way, a buffer area at least fifteen (15) feet in width plus five (5) additional feet in width for each ten (10) foot interval or fraction thereof of the height of the principal building exceeding twenty-five (25) feet. The buffer area shall consist of trees, fencing, earthen berm or any combination of same.