The Federal hazardous materials transportation law requires the Secretary of Transportation to ensure that, to the extent practicable, regulations governing the transportation of hazardous materials in commerce are consistent with standards adopted by international authorities (49 U.S.C. 5120(b)). Harmonization enhances safety, facilitates compliance, and improves the efficiency of the global transportation system by minimizing the regulatory burden on the public thus promoting trade. After a thorough review of the provisions recently adopted by various international regulatory bodies, PHMSA has identified areas in the Hazardous Materials Regulations (HMR) in which harmonization with international regulations will provide an enhanced level of safety, an economic benefit, or in many instances both increased safety and economic benefits. As a result, this rulemaking would amend the HMR, where appropriate, to maintain alignment with international standards that became effective as of January 1, 2023, and consequently facilitate the safe global trade of hazardous materials. Proposals in this rulemaking action would include, but are not limited to: Removal of the requirement to provide a telephone number (for additional information) on a lithium battery handling mark; exceptions from lithium battery test summary requirements for button cells installed in equipment; provisions for the design, construction, and use of fiber reinforced plastic portable tanks; and updates of International Organization for Standardization cylinder manufacturing and testing standards incorporated by reference.