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Hazmat Safety Community Pipeline Safety Community Briefing Room
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NTSB Safety Recommendations

The Pipeline and Hazardous Materials Safety Administration is required by law to respond to Safety Recommendations issued by the National Transportation Safety Board (NTSB), an independent federal agency charged by Congress with investigating significant hazardous materials accidents/incidents.

NTSB Classifications:

  • OAR - Open Acceptable Response
  • OAA - Open Acceptable Action
  • OAAR - Open Acceptable Alternative Action
  • OUA - Open Unacceptable Action
  • OUR - Open Unacceptable Response
  • UCL - Unclassified (until NTSB Classifies)


  • CAR - Closed Acceptable Response
  • CAA - Closed Acceptable Action
  • CAAA - Closed Acceptable Alternative Action
  • CAAR - Closed Acceptable Alternative Response
  • CNLA - Closed No Longer Applicable
  • CUA - Closed Unacceptable Action
  • CUR - Closed Unacceptable Response
National Transportation Safety Board
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