On May 11, 2020 (85 FR 27810) the Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a final rule to amend the Hazardous Materials Regulations (HMR) to maintain alignment with international regulations and standards by incorporating various amendments, including changes to proper shipping names, hazard classes, packing groups, special provisions, packaging authorizations, air transport quantity limitations, and vessel stowage requirements. These revisions are necessary to harmonize the HMR with recent changes made to the International Maritime Dangerous Goods Code, the International Civil Aviation Organization’s Technical Instructions for the Safe Transport of Dangerous Goods by Air, and the United Nations Recommendations on the Transport of Dangerous Goods—Model Regulations. Additionally, PHMSA is adopting several amendments to the HMR that would allow for increased alignment with the Transport Canada, Transportation of Dangerous Goods Regulations. DATES: Effective date: This rule is effective May 11, 2020, except for instruction 17, which is effective January 2, 2023. Voluntary compliance date: January 1, 2019. Delayed compliance date: May 10, 2021. Incorporation by reference date: The incorporation by reference of certain publications listed in this rule is approved by the Director of the Federal Register as of May 11, 2020.