USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

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
172.427 ORGANIC PEROXIDE label
172.442 CORROSIVE label
172.446 CLASS 9 label
172.447 LITHIUM BATTERY label
172.500 Applicability of placarding requirements
172.502 Prohibited and permissive placarding
172.503 Identification number display on placards
172.504 General placarding requirements
172.505 Placarding for subsidiary hazards
172.506 Providing and affixing placards: Highway
172.508 Placarding and affixing placards: Rail
172.510 Special placarding provisions: Rail
172.512 Freight containers and aircraft unit load devices
172.514 Bulk packagings
172.516 Visibility and display of placards
172.519 General specifications for placards
172.522 EXPLOSIVES 1.1, EXPLOSIVES 1.2 and EXPLOSIVES 1.3 placards
172.532 FLAMMABLE GAS placard
172.540 POISON GAS placard
172.542 FLAMMABLE placard
172.544 COMBUSTIBLE placard
172.550 OXIDIZER placard
172.556 RADIOACTIVE placard
172.558 CORROSIVE placard
172.560 CLASS 9 placard
172.600 Applicability and general requirements
172.602 Emergency response information
172.604 Emergency response telephone number
172.606 Carrier information contact
172.700 Purpose and scope
172.701 Federal-State relationship
172.702 Applicability and responsibility for training and testing
172.704 Training requirements
172.800 Purpose and applicability
172.802 Components of a security plan
172.804 Relationship to other Federal requirements
173.1 Purpose and scope
173.10 Tank car shipments
173.11 Exceptions for shipment of light bulbs containing hazardous materials
173.115 Class 2, Divisions 2.1, 2.2, and 2.3-Definitions
173.116 Class 2-Assignment of hazard zone
173.12 Exceptions for shipment of waste materials
173.120 Class 3-Definitions
173.121 Class 3-Assignment of packing group
173.124 Class 4, Divisions 4.1, 4.2 and 4.3-Definitions