Origin of Transport Regulations
The first edition of Transport Regulations was published in 1956, titled "Recommendations on the Transport of Dangerous Goods." Over the years it has evolved through regular biennial amendments. The 23rd revised edition (2023) is the edition currently implemented across the modal codes — IMDG Code 42-24 and ADR/RID/ADN 2025. A 24th revised edition was already adopted by the UN Sub-Committee in December 2024 and will feed the next round of modal updates.
UN Model Regulations has two parts: Recommendations on the Transport of Dangerous Goods and the Manual of Tests and Criteria (now in its 8th revised edition, including Amendment 1).
Implementation of Transport Regulations
The Orange Book is implemented through UN bodies and national governments into modal regulations:
| Body | Instrument | Current Edition | Mandatory From |
|---|---|---|---|
| IMO | IMDG Code | Amendment 42-24 | 1 Jan 2026 |
| ICAO | Technical Instructions (Air) | 2025–2026 Edition | 1 Jan 2025 (voluntary use permitted) |
| ECE | ADN (Inland Waterways) | ADN 2025 | 1 Jul 2025 |
| ECE | ADR (Road) | ADR 2025 | 1 Jul 2025 |
| OTIF | RID (Rail, Appendix C to COTIF) | RID 2025 | 1 Jul 2025 |
| USA | 49 CFR Parts 100–185 | Reflects 22nd ed. UN Model Regs / IMDG 41-22 (HM-215Q) | Catch-up NPRM pending (see note below) |
| Canada | TDG Regulations | 2023 Edition | — |
| Australia | ADG Code | On its own national cycle | — |
Unlike IMDG, ADR, RID and ADN, the HMR doesn't republish on the same two-year clock. The current Hazardous Materials Table still reflects the 22nd revised edition of the UN Model Regulations and IMDG 41-22, finalized under HM-215Q.
PHMSA published an NPRM in February 2026 proposing to bring the HMR up to the 23rd revised edition and IMDG 42-24 — including the new UN 3556 / 3557 / 3558 battery-powered vehicle entries — but as of this writing that rule is still proposed, not final. If you're cross-referencing IMDG 42-24 against 49 CFR today, expect a real gap on anything battery-vehicle related until that rulemaking closes.
Origin of GHS
GHS traces to the 1992 Rio Conference, developed jointly by the ILO, OECD, national governments and other stakeholders to harmonize classification criteria and labelling standards for chemicals.
The 1st edition of GHS (Purple Book) was published in 2005. The current edition is the 11th revised edition (2025).
Harmonization & Differences
IMDG Code 42-24 and ADR/RID/ADN 2025 are aligned with GHS 11th revised edition — IMDG 42-24 explicitly updated its Chapter 1.2 cross-reference from GHS Revision 9 to Revision 11 as part of this cycle.
Transport Regulations classify dangerous goods into 9 classes and environmentally hazardous substances, with some classes subdivided into divisions. GHS identifies substances, mixtures and articles into three groups: Physical Hazards, Health Hazards, and Environmental Hazards.
Where GHS and Transport Regulations Diverge
Not Covered by GHS
- Infectious substances
- Radioactive materials
- Other dangerous substances (elevated temperature substances, genetically modified microorganisms, lithium batteries, etc.)
Not Covered by Transport Regulations
- Eye damage / eye irritation
- Respiratory or skin sensitization
- Germ cell mutagenicity
- Carcinogenicity
- Reproductive toxicity
- Hazardous to the ozone layer
Have you aligned your SDS, Pictograms & Labels with GHS 11 and IMDG Code 42-24?
Contact UsDiscover more from IMDG Code Compliance Centre
Subscribe to get the latest posts sent to your email.