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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-19-0009 Elecsys Corporation Mr. Jamey Hilleary View
PI-16-0013 MarkWest Javelina Pipeline Company, LLC Ms. Leanne M. Meyer View
09-0013R Clean Harbors Environmental Services, Inc. Anthony Cellucci View
19-0051 The Hartford Steam Boiler Inspection and Insurance Co. Oberst Mulet View
19-0092 Total Compliance LLC Chris Heminger View
19-0095 Hazmat Resources, Inc Daniel Shelton View
19-0007 Association of American Railroads Robert E. Fronczak View
19-0055 Dangerous Goods Transport Consulting Inc. Frits Wybenga View
19-0081 North American Transportation Consultants William Herman View
19-0087 US Ecology, Inc. Michael Herron View
19-0099 ACA International LLC Tim Farrell View
19-0117 Railway Supply Institute (RSI) Mr. E. Michael O'Malley View
19-0047 Mr. Donald Brittingham View
PI-19-0001 Town of Hopkinton Mr. J. Raymond Miyares View
19-0033 Railsback Hazmat Safety Professionals, LLC Rex Railsback View
19-0066 Cryogenic Services, Ltd. Connor Orban View
19-0065 Freeman Manufacturing & Supply Company Ben Inman View
19-0054 Joseph Tsiyoni View
19-0014 Attorney at Law Lawrence W. Bierlein View
19-0060 Daniels Training Services, Inc. Daniel Stoehr View
19-0090 UL Materials and Supply Chain Kevin Skerrett View
19-0082 Thunder Creek Equipment Mr. Luke Van Wyk View
19-0040 Greenbrier Management Services James Rader View
19-0058 Mark Hawk View
19-0025 Robbie Dunn View
PI-19-0010 East Goshen Township Mr. Rick Smith View
19-0038 The Chemours Company Randolph Martin View
19-0074 ResinLab Andrea Florin View
19-0016 Advance Auto Parts Ryan Bodekor View
19-0070 VEGA Americas, Inc. Brett Kemphues View
19-0073 MISTRAS Group, Inc. David Boudreaux View
19-0017 John Christopher View
19-0072 C. Steinweg, Inc. John Moors View
19-0028 J.J. Keller and Associates, Inc. Thomas J. Ziebell View
19-0059 Midway USA Bradley Spears View
19-0069 HQ U.S. Army Europe Safety (AECS-S) Donald V. Paglioni View
19-0069 HQ U.S. Army Europe Safety (AECS-S) Mr.Donald Paglioni View
PI-18-0015 Pacific Energy and Mining Company Mr. Dan Green View
19-0024 AMTROL Water Systems David Beretta View
19-0049 Linde Gas North America Billy Stover View
19-0034 Mr. W. A. Winters View
19-0015 Bombardier Aerospace Jeff Christafore View
19-0043 Haley Hoewt View
18-0154 Commercial Vehicle Safety Alliance Collin B. Mooney View
19-0039 Landstar Transportation Logistics, Inc. Wes Pace View
19-0052 GSI Training Services, INc. Sam Burton View
19-0041 Dangerous Goods Advisory Council Del Billings View
PI-19-0005 New Terrain Technologies Mr. David Van der Vieren View
19-0046 Alloy Custom Products, LLC Evan Mills View
19-0005 Baker Petrolite, LLC David T. Hird View