This final rule provides that onshore "interstate pipeline facilities" (as that term is defined in the Hazardous Liquid Pipeline Safety Act of 1979) constructed before January 8,1971 may not transport highly volatile liquids (HVL) unless they have been , hydrostatically tested in accordance with Subpart E of Part 195 or do not operate at a pressure that exceeds 80 percent of any test or operating pressure which has been held for four continuous hours. This rule reduces the potential for severe HVL pipeline accidents caused by latent material and construction defects.