The UN Sub-Committee of Experts on the Transport of Dangerous Goods (TDG Sub-Committee) is tasked with maintaining and approving amendments to the United Nations Recommendations on the Transport of Dangerous Goods, also known as the UN Model Regulations. The UN Model Regulations serve as a basis for harmonized international and domestic dangerous goods transport regulations and are amended every two years.

The UN TDG Sub-Committee was established in 1954, and the first UN Model Regulations were published in 1956. The latest revision to the UN Model Regulation is the 22^nd Revised edition. The Model Regulations are available from the UN and several commercial sources.

PHMSA serves as the lead U.S. agency and works with the appropriate U.S. government stakeholders to develop consensus views. The U.S. also serves as TDG Sub-Committee chairman for the 2023-2024 biennium. Prior to TDG Sub-Committee meetings, PHMSA holds a public meeting to solicit input from stakeholders. All public meetings are announced via the Federal Register and on PHMSA's website.