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Section §172.502: Prohibited and permissive placarding

Below are the available interpretations and guidance for the given section. To return to the list of parts, use the Parts link above. If you do not see any guidance or interpretation information below, that means there is none available for the given part/section. Return to the search page to browse additional regulations sections.

PHMSA has published several Frequently Asked Questions (FAQ) documents on regulatory topics. Please review our FAQ documents below:

Additionally PHMSA has Hazardous Materials FAQs based on letters of interpretation on the following topics:

This section of the website provides the ability to find regulations information including regulations parts, content of sections, and interpretations for regulations sections. Below is a list of parts, identified by the part number and subject. 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.

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: 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.

The regulations text of the section can be found on the eCFR website. To view the regulations text, use the link below. For assistance, please send an email to

View section 172.502 on the ECFR website

Interpretation Responses

Ref ID Date Company Name Individual Name Response Document
22-0085 Aggreko Mr. Chad Thibodeaux View
22-0050 Mayo Clinic Mr. Travis Brandt View
22-0106 Clean Earth Nicholas Prevosti View
22-0024 Keller and Heckman, LLP Trent Doyle View
19-0128 Tyson Foods Carolyn Griffith View
19-0115 McAnally Wilkins Inc. Ray Miller View
18-0146 Texas Highway Patrol Brad Gibson View
07-0201 Q. A. Safety Mr. Ray L. Faucheux, Jr. View
11-0283 R & L Carriers, Inc. Mr. Gerald A. Krisa View
09-0184 CHS Transportation Mr. John Macpherson View
13-0120 Western International, Inc. Mr. David Ebbers P.E. View
99-0210 Marsulex, Inc. Sam Reeder, PhD View
11-0298 Public Utilities Commission of Ohio Transportation Department Compliance Division Mr. Tom Forbes View
00-0252 Mr. Thomas Dutkiewicz View
12-0150 Horizon Lines Mr. Clifford Bartley View
02-0102 Motor Transport Association of Connecticut, Inc Michael J. Riley View
99-0205 R & L Transfer, Inc. Mr. Randy Russell View
14-0031 YRC Freight, Inc. Ms. Susan D. Camara View
11-0181 McAda Fluids Heating Services Mr. James S. McAda View
09-0224 URS Ms. Erin N. Jarman View
15-0013 Pinnacle Propane Mr. Kyle Sparks View
12-0139 Nebraska State Patrol Sergeant Brad Wagner View
02-0211 Minnesota Department of Transportation, Office of Motor Carrier Services Michael Ritchie View
02-0230 Georgia Department of Motor Vehicle Safety, Law Enforcement Division Captain Bruce Bugg View
12-0246 AWP, Inc. Mr. Eric A. Hulme View
12-0188 Enservco Mr. Don Custer View
06-0108 Con-way Mr. Robert Petrancosta  View
16-0058 Nebraska State Patrol Mr. Brad Wagner View
11-0102 Texas Department of Public Safety Texas Highway Patrol/Commercial Vehicle Enforcement Mr. Patrick B. Zatopek View
13-0230 Universal Well Services, Inc. Mr. Tom Cloud View
02-0248 Nebraska State Patrol, Carrier Enforcement Division Sergeant Brad Wagner View
15-0024 Hazardous Materials Response Unit Officer Daniel Voelker View
04-0191 Georgia Department of Motor Vehicle Safety Captain Bruce Bugg View
10-0099 Sporting Arms & Ammunition Manufacturers Institute, Inc. Mr. Rick Patterson View
00-0101 Mayer, Brown & Platt Mr. Philip R. Recht View
15-0128 Ground Up Road Construction Inc. Scott Stultz View