A nonconforming use, if changed to a conforming use, shall not thereafter be changed back to any nonconforming use. A nonconforming use may, by special exception, be changed to another nonconforming use, provided that the Zoning Hearing Board shall find that the proposed use is less intense than the prior use. Such intensity shall be measured by the extent of lot coverage, parking, traffic impact, noise pollution, air pollution, safety and other area and bulk regulations.