PHMSA
PHMSA — Letters of Interpretation
How PHMSA has answered questions about the hazmat rules, and how to request your own letter.
PHMSA’s written answers to questions about the hazmat rules, and how to request a letter of your own.
Open it when the regulation reads two ways and you need to know how PHMSA has read it. Each letter answers the facts it was asked about, so check that your situation matches before you lean on one.
The regulation still governs. An interpretation explains it; it doesn’t replace it.