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Letters of Interpretation

PHMSA has published several Frequently Asked Questions (FAQs) documents on programmatic topics. Please review these documents here at: https://www.phmsa.dot.gov/about-phmsa/phmsa-faqs.

Additionally, Office of Hazardous Materials Safety has published Hazardous Materials FAQs based on letters of interpretation on the following topics:

Office of Hazardous Materials Safety: For questions about transporting hazardous materials, needing clarifications of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180), or requesting a formal letter of interpretation, please go to the Hazardous Materials Information Center (HMIC) page for contact information (phone and email address). Pending interpretation letters that are under review by the Office of Hazardous Materials Safety can be found at Pending Hazardous Materials (Hazmat) Interpretations.  

Office of Pipeline Safety: A written regulatory interpretation, response to a question, or an opinion concerning a pipeline safety issue may be obtained by submitting a written request to the Office of Pipeline Safety (PHP–30), PHMSA, U.S. Department of Transportation, 1200 New Jersey Avenue SE., Washington, DC 20590–0001 or at the email address: pipeline_interp_submittal@dot.gov. In addition to email address, the requestor must include his or her return address and should also include a daytime telephone number. Requests should be submitted at least 120 days before the time the requestor needs a response. Note: electronic submission is provided as alternative to the 49 CFR Part 190.11(b) mail-in requirement.

Interpretation letters under review are available at the Office of Pipeline Safety’s Interpretation Review page. To submit comments on an interpretation under review, proceed to the Interpretation Review page, locate the interpretation to comment on, and click the appropriate link to submit a comment on the corresponding interpretation. Comment submissions will be accepted for 30-days after the interpretation letter is posted.

This section of the website below provides the ability to find regulations information including regulations parts, content of sections, and interpretations for regulations sections. A list of parts, identified by the part number and subject is also provided. To browse sections by part, click on the subject link below. You will be taken to the eCFR website to view sections for a part.

The eCFR is also searchable by keyword and other available options on the eCFR website. To search and browse regulations using the eCFR website, use the link below. For assistance, please send an email to PHMSA.Webmaster@dot.gov.

Search the eCFR

Interpretations Reference #

Search Tip: Use quotation marks to search for commonly used phrases, such as “gas transmission” or “cargo tank motor vehicle.”
E.g., 02/09/2021
E.g., 02/09/2021
Ref ID: Date Company Name Individual Name Response Document
PI-79-028 Alaska Pipeline Office Morris J. Turner View
PI-79-027 Leo L. Andrews View
PI-79-025 Offshore Operators Committee L. G. Otteman View
PI-79-026 Energy Regulatory Commission E. Scott Smith View
PI-79-024 John E. Good Associates John E. Good View
PI-79-023 NIBCO Inc. Don Wagoner View
PI-79-022 Kansas Public Service Company, Inc. William C. Salone, III View
PI-79-021 North Central Public Service Co. Robert R. Kain View
PI-79-020 Memo: Internal View
PI-79-019 John Parker View
PI-79-017 Union Oil Company of California Ted Russell View
PI-79-018 Columbia Gulf Transmission Company Kathleen O'Leary View
PI-79-016 Exchange Oil & Gas Corporation Peter R. Monrose View
PI-79-0102 View
PI-79-015 El Paso Natural Gas Company Foch LaFitte View
PI-79-014 Aguirre & Dabney AIA Architects Pedro Aguirre, Jr. View
PI-79-013 Memo: Internal View
PI-78-011 Borg-Warner Corporation Mr. Jim C. Hallmark View
PI-79-012 Borg-Warner Corporation Jim C. Hallmark View
PI-79-010 Memo: Internal View
PI-79-008 Patton, Boggs and Blow J. Gordon Arbuckle View
PI-79-007 Quality Systems Incorporated John C. Wormeli View
PI-79-005 Memo: Internal View
PI-79-004 House of Representatives Honorable Trent Lott View
PI-79-0101 View
PI-79-003 Continental-Emsco Company Gary Faulkenberry View
PI-79-002 Arizona Corporation Commission H.R. Garabrant View
PI-79-0100 View
PI-78-033 Memo: Internal View
PI-78-034 Gas Pipeline Safety Division Mr. T. K. Spalding View
PI-78-030 Illinois Commerce Commission Mr. Harold E. Shutt View
PI-78-0110 View
PI-78-0109 View
PI-78-028 Memo: Internal View
PI-78-027 Memo: Internal View
PI-78-0108 View
PI-78-0107 View
PI-78-025 Arkansas Louisiana Gas Company Mr. James C. Baker View
PI-78-024 Clanton & Johnson Mr. John W. Johnson View
PI-78-0106 View
PI-78-0105 View
PI-78-0104 View
PI-78-021 Union Oil Company of California Mr. Calvin F. Broussard View
PI-78-020 The University of Tennessee Professor Charles L. Thompson View
PI-78-019 LAVALCO Pipeline Products Division Mr. James H. Thompson, View
PI-78-018 LAVALCO Pipeline Products Division Mr. James H. Thompson, View
PI-78-017 various various View
PI-78-016 National LP-Gas Association Mr. Daniel N. Myers View
PI-78-015 The Australian Gas Light Company Mr. C. B. Rumble View
PI-78-014 County of Harris Mr. Richard P. Doss View