The IMDG Code governs dangerous goods carried by sea, ADR governs carriage by road, and 49 CFR (the US Hazardous Materials Regulations) covers all modes of transport in the United States. All three are based on the UN Model Regulations, so classification, UN numbers and packing groups are largely shared, but the detail differs. If a shipment changes mode or crosses a border, it will often need to comply with more than one of them.
Who publishes each set of rules
IMDG Code (sea)
The International Maritime Dangerous Goods (IMDG) Code is published by the International Maritime Organization (IMO). It covers dangerous goods in packaged form carried by sea, and is made mandatory through SOLAS Chapter VII, with MARPOL Annex III covering marine pollution. IMO amends the Code every two years. The 2024 Edition (Amendment 42-24) became mandatory on 1 January 2026. In the UK, it is given legal effect by the Merchant Shipping (Dangerous Goods and Marine Pollutants) Regulations 1997.
ADR (road)
ADR, the Agreement concerning the International Carriage of Dangerous Goods by Road, is administered by the United Nations Economic Commission for Europe (UNECE). ADR itself has no enforcement provisions, so each country gives it legal force through national law. In Great Britain this is done by the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009 (CDG Regs), which currently implement ADR 2025.
49 CFR (United States, all modes)
Title 49 of the Code of Federal Regulations, Parts 171 to 180, contains the Hazardous Materials Regulations (HMR), issued by the US Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA). Unlike the IMDG Code and ADR, the HMR are a single rulebook for highway, rail, air and vessel transport, with separate parts for each mode (Part 176 for vessels, Part 177 for highway). The HMR say “hazardous materials” rather than “dangerous goods”.
How the three are structured
The IMDG Code and ADR both follow the UN Model Regulations layout: numbered parts covering general provisions, classification, the dangerous goods list (Table A in ADR), packing, consignment procedures, packaging and operations. IMDG Part 7 covers stowage and segregation on board ship. ADR Parts 7 to 9 cover carriage, vehicle crews and vehicles.
49 CFR is organised differently. Part 172 contains the Hazardous Materials Table (§ 172.101) plus shipping papers, marking, labelling, placarding and training. Part 173 covers classification and packaging, and Parts 174 to 177 cover each mode.
When more than one set of rules applies
A container of paint shipped from Birmingham to Houston might go by road under ADR to a UK port, by sea under the IMDG Code, then by truck or rail in the US. Each leg must meet the rules for that mode and territory.
Using the IMDG Code in the United States
49 CFR Part 171, Subpart C, allows certain international standards, including the IMDG Code, to be used in the US, with conditions:
- § 171.22 authorises shipments made under the IMDG Code, provided they also meet that subpart. US requirements on emergency response information, training (including function-specific training in the international standard used), security, incident reporting and registration still apply. A shipper’s certification (§ 172.204) is required, and US shipping papers and markings must be in English.
- § 171.23 sets requirements for specific materials and packagings, such as cylinders, shipped under international standards.
- § 171.25 allows hazardous materials to be transported to, from or within the US by vessel, motor carrier and rail in accordance with the IMDG Code, provided all or part of the movement is by vessel. Road and rail legs must still meet Parts 177 and 174, and vehicles must be placarded under Part 172, Subpart F. For vessel transport, IMDG Part 7 stowage and segregation may be used instead of Part 176. § 171.25(d) also covers use of the IMDG Code within a single US port area.
Common differences that catch shippers out
Marine pollutants
The IMDG Code requires marine pollutants to be identified, marked and declared. 49 CFR also regulates marine pollutants (§ 171.4), based on MARPOL Annex III. However, it exempts non-bulk packagings carried by road, rail or air unless part of the journey is by vessel. ADR uses an environmentally hazardous substance mark for goods that meet its environmental criteria.
Classification scope
The nine hazard classes are the same in all three, but the boundaries differ. For example, 49 CFR regulates “combustible liquids” with a flash point above 60 °C and below 93 °C (§ 173.120(b)). This category has no direct equivalent in the IMDG Code or ADR.
Segregation
The IMDG Code has detailed segregation rules for stowage on board ship. ADR uses mixed-loading prohibitions for road vehicles. The HMR use a segregation table for highway transport and Part 176 for vessels.
Documentation
All three require a dangerous goods transport document showing the UN number, proper shipping name, class and packing group. The IMDG Code adds sea-specific items, including marine pollutant identification and a container or vehicle packing certificate. 49 CFR requires a shipper’s certification and emergency response information, including a telephone number. ADR also requires instructions in writing to be carried in the vehicle cab.
Training
49 CFR is the most prescriptive: § 172.704 requires general awareness, function-specific, safety and security awareness training, completed within 90 days for new employees, repeated at least every three years and recorded. ADR requires training under Chapter 1.3, a separate driver training certificate, and, for many businesses, a Dangerous Goods Safety Adviser (ADR 1.8.3). The IMDG Code sets training requirements in Chapter 1.3.
Comparison at a glance
| IMDG Code | ADR | 49 CFR (HMR) | |
|---|---|---|---|
| Mode | Sea (packaged goods) | Road | All modes in the US |
| Published by | IMO | UNECE | US DOT / PHMSA |
| Legal basis | SOLAS Ch. VII and MARPOL Annex III, via national law | International agreement, via national law (CDG Regs 2009 in GB) | US federal regulation |
| Current version | Amendment 42-24, mandatory from 1 January 2026 | ADR 2025 | Amended by federal rulemaking |
| Main list | Dangerous Goods List | Table A | Hazardous Materials Table (§ 172.101) |
| Segregation | Stowage and segregation (Part 7) | Mixed-loading prohibitions | Highway table; Part 176 or IMDG Part 7 for vessels |
| Marine pollutants | Regulated and marked | Environmentally hazardous mark | § 171.4; non-bulk exempt unless part of journey is by vessel |
| Training | Chapter 1.3 | Chapter 1.3, driver training, DGSA | § 172.704; recurrent every three years |
How Hazcheck can help
Hazcheck Search lets you look up substance data across the IMDG Code, 49 CFR and ADR, and Hazcheck Validate checks dangerous goods bookings against all three before cargo is accepted. The ADR/IMDG Code Interface Course covers the road-to-sea handover, alongside the ADR Standard Course, IMDG Code e-learning and the Dangerous Goods Transport General Awareness Course. Contact us to discuss your needs.
Frequently asked questions
Can I ship to the US under the IMDG Code instead of 49 CFR?
Often, yes. 49 CFR § 171.25 allows transport under the IMDG Code where all or part of the movement is by vessel, subject to the conditions in §§ 171.22 to 171.25. Some US requirements still apply.
Does ADR apply outside the European Union?
Yes. ADR is a UNECE agreement, not EU law, and its contracting parties include non-EU countries. Each country applies it through its own legislation.
Are the hazard classes the same in all three?
Yes, the nine classes are harmonised through the UN Model Regulations, so a substance normally has the same class, UN number and packing group. Differences come from scope, special provisions and exceptions.
Do I need training in each regulation?
You need training in the rules that apply to your job. 49 CFR § 171.22(g)(2) requires function-specific training in any international standard used in the US, so someone sending sea shipments from Europe to the US may need ADR, IMDG Code and 49 CFR training.
Sources
- IMO – Dangerous goods
- IMO Publishing – IMDG Code, 2024 Edition
- MCA – MSN 1914 (M): The carriage of dangerous goods and marine pollutants
- HSE – ADR, CDG Regs and Dangerous Goods Safety Advisers
- HSE – Carriage of dangerous goods: introduction
- eCFR – 49 CFR Part 171, Subpart C (§§ 171.22–171.25)
- eCFR – 49 CFR § 171.4 Marine pollutants
- eCFR – 49 CFR § 172.704 Training requirements
- eCFR – 49 CFR § 173.120 Class 3 definitions