PHMSA letter of interpretation

ICAO TI segregation

Pipeline and Hazardous Materials Safety Administration · Jul 31, 2008 · Reference No. 08-0168

Interprets: 49 CFR § 171.11

Reggie’s quick take

PHMSA retracted a 1993 letter that had said hazmat shipped under the ICAO Technical Instructions could follow either ICAO segregation rules or Part 177 when it moved by motor vehicle before or after an air leg. That was wrong. Under § 171.24(c), as added by the 2007 HM-215F rule, shipments moving by highway before or after air transport must follow Part 177 segregation rules.

Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.

Our May 28, 1993 letter responded to a request by your company for clarification on the use of the International Civil Aviation Organization Technical Instructions (ICAO TI) under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, we responded that hazardous materials transported in accordance with ICAO TI, as authorized by § 171.11, in motor vehicles prior to or after transport by aircraft may be segregated in accordance with ICAO TI or Part 177 of the HMR. The guidance is incorrect and therefore, we are retracting our letter and issuing this correction.

Hazardous materials prepared in accordance with ICAO TI and transported in motor vehicles prior to or after transport by aircraft must conform to the highway segregation requirements of Part 177, Carriage by Public Highway. PHMSA revised and consolidated requirements authorizing the use of international standards and regulations in a final rule under Docket HM-215F (72 FR 25161; May 3, 2007). Among the revisions of the rulemaking, we added language for the use of the ICAO TI clarifying the applicability of Part 177. Section 171.22 authorizes the offering for transport or transportation of hazardous materials in commerce to, from, or within the United States in accordance with international standards and regulations, including the ICAO TI. Section 171.24 provides additional requirements for the use of ICAO TI including requirements for highway transportation. Specifically, § 171.24(c) requires shipments transported by highway prior to or after transportation by aircraft to conform to the applicable requirements of Part 177.

A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.