ADR orange plates explained

You pass lorries with orange plates on the motorway every day. To most people they’re just warning signs. Read the two numbers, though, and you know straight away which substance is on board and what hazard it poses. That’s why vehicle markings are part of the ADR core module.

What the plate looks like

The plate is orange, rectangular and reflective. It is 40 cm wide and 30 cm high, with a black border 15 mm wide (ADR 5.3.2.2.1). If the vehicle doesn’t have enough space for a plate that size, it can be made smaller, down to 300 × 120 mm with a 10 mm border.

On a numbered plate, a horizontal black line 15 mm thick runs across the middle and separates the two numbers. The digits are black, 100 mm high, with a stroke thickness of 15 mm (ADR 5.3.2.2.2). The plate and the numbers have to survive 15 minutes engulfed in fire: the plate must not come away from its mount, and the numbers must still be legible afterwards.

Hazard number and UN number

The top number is the hazard identification number, or hazard number for short. The bottom one is the UN number.

The UN number has four figures and identifies the substance or article. You look it up in Chapter 3.2, Table A of ADR. 1203, for example, is MOTOR SPIRIT or GASOLINE or PETROL.

The hazard number is made up of two or three figures (ADR 5.3.2.3.1). In general, each figure stands for one hazard:

Figure	Meaning
2	Emission of gas due to pressure or to chemical reaction
3	Flammability of liquids (vapours) and gases or self-heating liquid
4	Flammability of solids or self-heating solid
5	Oxidizing (fire-intensifying) effect
6	Toxicity or risk of infection
7	Radioactivity
8	Corrosivity
9	Risk of spontaneous violent reaction

On top of that, there are a few rules you’ll need for the exam:

• Doubled figure: the hazard is more intense. 33 means a highly flammable liquid with a flash-point below 23 °C.
• Figure followed by a zero: if one figure is enough to describe the hazard, a 0 is added after it. 80 is a corrosive or slightly corrosive substance.
• X in front of the number: the substance reacts dangerously with water. Water may then only be used with the approval of experts.
• Special combinations: some numbers have a meaning of their own, such as 22 (refrigerated liquefied gas, asphyxiant) or 90 (environmentally hazardous substance; miscellaneous dangerous substances). The full list is in ADR 5.3.2.3.2.
• Class 1: there’s no hazard number made of figures. The classification code from Table A goes in its place, made up of the division number and the compatibility group letter, for example 1.1D.

Where the plates go

A transport unit carrying dangerous goods displays two orange plates, one at the front and one at the rear. They sit at right angles to the length of the vehicle and must be clearly visible (ADR 5.3.2.1.1). If a trailer carrying dangerous goods is uncoupled during the journey, a plate stays on its rear.

For goods in packages, these two plates normally stay blank. ADR asks for numbers mainly on tanks and bulk loads. If Table A gives the substance a hazard number in column (20), a tanker also carries numbered plates on the sides of each tank or tank compartment, parallel to the length of the vehicle (ADR 5.3.2.1.2). The plates at the front and rear can then stay blank. Solids carried in bulk get their numbered plates on the sides of the vehicle or container (ADR 5.3.2.1.4).

Two exceptions let you leave off the side plates and show the numbers at the front and rear instead:

• One substance only: if the transport unit carries just one dangerous substance and nothing that isn’t dangerous, numbered plates at the front and rear are enough (ADR 5.3.2.1.6). A tanker carrying only sulphuric acid then shows 80 over 1830 at both ends.
• Fuels and heating oil: a tanker carrying only UN 1202, 1203, 1223 or 3475, or aviation fuel under UN 1268 or 1863, can run without side plates as long as the front and rear plates show the right numbers. With UN 3475 on board, they show the numbers for UN 3475. Otherwise they show those of the most hazardous substance, meaning the one with the lowest flash-point (ADR 5.3.2.1.3). UN 3475, an ethanol and petrol mixture, has been on this list since ADR 2025.

When no plates are needed

Not every load of dangerous goods needs orange plates:

• Small loads in packages: ADR 1.1.3.6 caps the quantity per transport unit according to the transport category in column (15) of Table A. For mixed loads, each quantity is multiplied by a factor and the results are added up, and the total must not exceed 1,000 (ADR 1.1.3.6.4). That’s where the name ‘1,000 points rule’ comes from. Below the limit, Chapter 5.3 doesn’t apply, so no plates are required (ADR 1.1.3.6.2). This only works for packages, never for tanks or bulk.
• Limited quantities (LQ): Chapter 5.3 doesn’t apply to goods packed under Chapter 3.4 (ADR 3.4.1). A transport unit with a maximum mass over 12 tonnes that carries more than 8 tonnes gross of LQ packages displays the LQ mark at the front and rear instead, at least 250 × 250 mm (ADR 3.4.13 to 3.4.15).
• Excepted quantities (EQ): only a few ADR provisions apply to goods carried under Chapter 3.5, and marking the vehicle isn’t one of them (ADR 3.5.1.1).

LQ and EQ goods don’t count towards the 1.1.3.6 limits (ADR 1.1.3.6.5).

Everyday examples

Put it into practice

Always read the plate from top to bottom: first the danger, then the substance. A handful of practice questions and it will stick.

In the free test you get an explanation and the ADR reference after every answer. In the app you can also mark up a vehicle yourself with plates and placards.

Sources

ADR 2025: the definition of ‘UN number’ in 1.2.1, sub-sections 1.1.3.6 and 5.3.2.1 to 5.3.2.3, Chapters 3.4 and 3.5, and Chapter 3.2, Table A. The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009, regulation 6 and Schedule 1. This guide explains the basics. When you mark an actual load, the wording of ADR and the CDG Regulations is what counts.