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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

49 CFR Parts 100-199

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

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 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

Search the eCFR

E.g., 02/09/2021
E.g., 02/09/2021
Part/Section Subject
177.848 Segregation of hazardous materials
177.854 Disabled vehicles and broken or leaking packages; repairs
178.2 Applicability and responsibility
178.273 Approval of Specification UN portable tanks
178.274 Specifications for UN portable tanks
178.274 Specifications for UN portable tanks
178.275 Specification for UN Portable Tanks intended for the transportation of liquid and solid hazardous materials
178.277 Requirements for the design, construction, inspection and testing of portable tanks intended for the transportation of refrigerated liquefied gases
178.3 Marking of packagings
178.320 General requirements applicable to all DOT specification cargo tank motor vehicles
178.33 Specification 2P; inner nonrefillable metal receptacles
178.33-7 Wall thickness
178.33-9 Marking
178.337 Specification MC 331; cargo tank motor vehicle primarily for transportation of compressed gases as defined in subpart G of part 173 of this subchapter
178.337-1 General requirements
178.337-10 Accident damage protection
178.337-11 Accident damage protection
178.337-16 Testing
178.337-17 Marking
178.337-18 Certification
178.337-3 Structural integrity
178.337-8 Openings, inlets, and outlets
178.337-9 Pressure relief devices, piping, valves, hoses, and fittings
178.338-10 Accident damage protection
178.338-16 Inspection and testing
178.33a Specification 2Q; inner nonrefillable metal receptacles
178.33a-8 Tests
178.33b-5 Material
178.33b-7 Design qualification test
178.33b-9 Marking
178.345 General design and construction requirements applicable to Specification DOT 406 (178.346), DOT 407 (178.347), and DOT 412 (178.348) cargo tank motor vehicles
178.345-1 General requirements
178.345-10 Pressure relief
178.345-11 Tank outlets
178.345-14 Marking
178.345-15 Certification
178.345-2 Material and material thickness
178.345-3 Structural integrity
178.345-5 Manhole assemblies
178.345-7 Circumferential reinforcements
178.345-8 Accident damage protection
178.345-9 Pumps, piping, hoses and connections
178.346-3 Pressure relief
178.347 Specification DOT 407; cargo tank motor vehicle
178.347-1 General requirements
178.347-4 Pressure relief
178.347-5 Pressure and leakage test
178.348 Specification DOT 412; cargo tank motor vehicle
178.348-1 General requirements