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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 Part 174 on the ECFR website

Regulation Sections

Section Subject
174.1 Purpose and scope
174.2 Limitation on actions by states, local governments, and Indian tribes
174.3 Unacceptable hazardous materials shipments
174.5 Carrier's materials and supplies
174.9 Safety and security inspection and acceptance
174.14 Movements to be expedited
174.16 Removal and disposition of hazardous materials at destination
174.20 Local or carrier restrictions
174.24 Shipping papers
174.26 Notice to train crews
174.50 Nonconforming or leaking packages
174.55 General requirements
174.57 Cleaning cars
174.59 Marking and placarding of rail cars
174.61 Transport vehicles and freight containers on flat cars
174.63 Portable tanks, IM portable tanks, IBCs, Large Packagings, cargo tanks, and multi-unit tank car tanks
174.67 Tank car unloading
174.81 Segregation of hazardous materials
174.82 General requirements for the handling of placarded rail cars, transport vehicles, freight containers, and bulk packages
174.83 Switching placarded rail cars, transport vehicles, freight containers, and bulk packagings
174.84 Position in train of loaded placarded rail cars, transport vehicles, freight containers or bulk packagings when accompanied by guards or technical escorts
174.85 Position in train of placarded cars, transport vehicles, freight containers, and bulk packagings
174.86 Maximum allowable operating speed
174.101 Loading Class 1 (explosive) materials
174.102 Forbidden mixed loading and storage
174.103 Disposition of damaged or astray shipments
174.104 Division 1.1 or 1.2 (explosive) materials; car selection, preparation, inspection, and certification
174.105 Routing shipments, Division 1.1 or 1.2 (explosive) materials
174.106 'Order-Notify' or 'C.O.D.' shipments, Division 1.1 or 1.2 (explosive) materials
174.110 Car magazine
174.112 Loading Division 1.3 materials and Division 1.2 (explosive) materials (Also see 174.101)
174.114 Record to be made of change of seals on 'Cars loaded with Division 1.1 or 1.2 (explosive) materials'
174.115 Loading Division 1.4 (explosive) materials
174.200 Special handling requirements
174.201 Class 2 (gases) material cylinders
174.204 Tank car delivery of gases, including cryogenic liquids
174.290 Materials extremely poisonous by inhalation shipped by, for, or to the Department of Defense
174.300 Special handling requirements
174.304 Class 3 (flammable liquid) materials in tank cars
174.31 Requirements for the operation of high-hazard flammable trains
174.600 Special handling requirements for materials extremely poisonous by inhalation
174.615 Cleaning cars
174.68 Division 6.1 (poisonous) materials with foodstuffs
174.700 Special handling requirements for Class 7 (radioactive) materials
174.715 Cleanliness of transport vehicles after use
174.750 Incidents involving leakage