ADR explained: the 9 classes of dangerous goods

ADR shipments fail most often for a simple reason: the load is physically ready, but the paperwork, labels, or handling plan isn’t. In France, that can mean a refusal at pickup, a blocked delivery at the gate, or a delay while the carrier tries to reconcile missing data. The fastest way to avoid that is to treat ADR as an operational workflow: correct classification, clean documentation, and a plan that matches the vehicle, route, and site constraints.

This primer explains what ADR is, the nine classes at a glance, what documents and labels you typically need, and the practical pitfalls that cause refusals—without getting lost in legal jargon.

What is ADR and when does it apply?

ADR is the European agreement that governs the international carriage of dangerous goods by road. At EU level, the dangerous goods framework is aligned with the UN list and incorporated into the ADR annexes.

In France, ADR/RID/ADN rules are implemented through the national “arrêté TMD” (order of 29 May 2009 on transport of dangerous goods by land), which applies the transport code and transposes the EU directive on inland transport of dangerous goods.

Operationally, ADR applies when your goods are classified as dangerous for transport (e.g., flammable liquids, corrosives, certain batteries) and the move is not covered by a specific exemption. Exemptions exist (e.g., limited/excepted quantities and other thresholds), but you should treat them as carrier- and lane-sensitive and confirm before dispatch.

The 9 ADR classes (fast overview)

ADR groups dangerous goods into nine classes (some with divisions). UNECE’s ADR classification part lists them as Classes 1 to 9.

Table: Class → common examples → key controls (ops view)

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(Classes 4, 5 and 6 include divisions; your exact controls depend on the assigned UN number and packing instructions.)

What documents and labels do you need?

Think in three layers: the transport document, the vehicle/driver documents, and the package/vehicle marking. The exact list depends on the shipment type, but French control leaflets highlight common requirements: an ADR-compliant transport document (ADR 5.4.1) and written instructions (ADR 5.4.3), plus driver training proof where required.

1) The ADR transport document

The form isn’t always prescribed, but the content is. A practical reference list for what’s commonly required in sequence includes: UN number, proper shipping name, class, packing group (if applicable) and tunnel restriction code, plus shipper/consignee details. This document must match your labels and your booking data. Most “refused loads” come from mismatches (wrong UN number, missing packing group, inconsistent quantities).

2) Written instructions and driver/vehicle papers

Written instructions are part of the safety set, alongside required driver credentials for dangerous goods. If you move DG regularly, align internally on who provides what: the shipper provides the correct classification/data and shipment paperwork; the carrier ensures the vehicle/driver compliance for the move.

3) Labels, markings, and UN packaging

Packages must carry the correct hazard labels and markings, including the UN number where required; labeling is a core requirement and must be legible and durable. Where UN-approved packaging is required, ensure the packaging is suitable for the assigned packing instruction and the product’s hazards.

Template: ADR “data block” (paste-ready)

Use this block in your booking, transport document draft, and internal handover notes:

• UN number + Proper Shipping Name:
• ADR class / division + subsidiary risk (if any):
• Packing group (if applicable):
• Tunnel restriction code (if applicable):
• Quantity + packaging type: (e.g., 12 cartons, 1 pallet)
• Net/gross weight (kg) and number of handling units:
• Special provisions / temperature constraints (if any):
• Emergency contact / instructions location:
• Shipper + consignee full addresses + PO/booking reference:

Operational pitfalls (packaging, segregation, vehicle, training)

Most ADR incidents are avoidable because they’re process-related.

Pitfall 1: Wrong or incomplete data. If the UN number, class, packing group or tunnel code is wrong, the carrier may refuse the load, or the shipment may be stopped during checks. Build pre-dispatch validation and require evidence for any “exemption” claim.

Pitfall 2: Packaging that doesn’t survive handling. ADR doesn’t remove real-world freight forces: vibration, stacking pressure, and terminal handling. If cartons collapse or leak, you’ve created a safety event. Use packaging discipline from your standard freight playbook: correct box strength, proper sealing, no overhang on pallets, and clear “upright” orientation where needed.

Pitfall 3: Incompatible mixed loads / segregation gaps. Some DG combinations can’t travel together, or they require separation. Don’t assume “one pallet is fine.” Confirm compatibility rules with the carrier and document the loading plan.

Pitfall 4: Site readiness and training gaps. Loading/unloading staff must know what they’re handling. French references emphasize qualified personnel for handling operations in regulated contexts.
If your site frequently ships ADR, treat training and role clarity as a permanent control, not a one-off exercise.

Pitfall 5: Route constraints and tunnels. Tunnel restriction codes matter operationally: the “fastest” route may be forbidden. Make route feasibility checks part of planning, especially for urban deliveries and cross-border lanes.

“Before booking ADR” checklist

Before you book, confirm: the correct UN/classification is agreed and documented; packaging and labels match the classification; the transport document can be generated from consistent data; pickup and delivery sites can accept ADR; and the carrier confirms vehicle/driver readiness for the lane and any route restrictions. (If any part is “uncertain,” resolve it before dispatch – ADR problems don’t get easier on the road.)

Frequently Asked Questions (FAQ)

Do I need ADR for small quantities?

Sometimes exemptions apply (e.g., limited/excepted quantity frameworks and other thresholds), but the operational rule is: don’t assume. Validate with your carrier based on the exact UN number, packaging, quantity, and route. Misapplying an exemption is a common reason for refusal or delays.

What’s the #1 cause of refusal?

Wrong or missing documentation and labeling. Controls and guidance emphasize that ADR transport is accompanied by a compliant transport document and the required safety documents. If the label doesn’t match the document, or the required fields are missing, the carrier may refuse pickup—or the shipment may be held during checks.

Who is responsible?

Responsibility is shared across the chain. France implements ADR through national TMD regulation and expects each party to meet its obligations (shipper, carrier, loader/unloader). Practically, shippers must provide correct classification/data and compliant packaging/labels; carriers must ensure compliant transport execution (vehicle/driver requirements and safe operations).