ADR tunnel restrictions: categories and tunnel codes
Each tunnel has a category from A to E and your load has a tunnel code. Here is how to tell whether you can drive through.
In this guide
Before a tunnel, a driver carrying dangerous goods has to match two letters: the tunnel's category and the tunnel restriction code of the load. The category is set by the competent authority of the country where the tunnel is, based on a risk assessment and the alternative routes available (1.9.5.1). The same tunnel can be in a different category by day and by night, or at weekends. Here's how to read both letters under ADR 2025.
Five tunnel categories
Categories are based on three hazards that can cause many casualties or serious damage to a tunnel: explosions, the release of toxic gas or volatile toxic liquid, and fires (1.9.5.2.1).
| Cat. | Restriction applies to (1.9.5.2.2) |
|---|---|
| A | no restrictions for dangerous goods |
| B | goods that may lead to a very large explosion |
| C | as B, plus goods that may lead to a large explosion or a large toxic release |
| D | as C, plus goods that may lead to a large fire |
| E | all dangerous goods except those coded "(-)", plus limited quantities above 8 tonnes gross per transport unit |
The further down the alphabet, the stricter the tunnel. Category E lets the fewest placarded vehicles through.
Where to find the tunnel code
The tunnel restriction code is in column (15) of Table A in Chapter 3.2, at the bottom of the cell, in brackets (8.6.3.1). The consignor copies it onto the transport document as the last part of the description, for example "UN 1203 PETROL, 3, II, (D/E)" (5.4.1.1.1 k).
When a transport unit carries goods with different codes, the most restrictive code applies to the whole load (8.6.3.2).
What the code means: the table in 8.6.4
The part before the slash applies to carriage in tanks, and for D/E to bulk carriage as well. The part after the slash covers all other carriage, which usually means packages.
| Code | Passage forbidden through tunnels of category |
|---|---|
| B | B, C, D and E |
| B1000C | net explosive mass over 1000 kg: B, C, D and E; up to 1000 kg: C, D and E |
| B/D | tanks: B, C, D and E; other carriage: D and E |
| B/E | tanks: B, C, D and E; other carriage: E |
| C | C, D and E |
| C5000D | net explosive mass over 5000 kg: C, D and E; up to 5000 kg: D and E |
| C/D | tanks: C, D and E; other carriage: D and E |
| C/E | tanks: C, D and E; other carriage: E |
| D | D and E |
| D/E | bulk or tanks: D and E; other carriage: E |
| E | E |
| (-) | passage allowed through all tunnels |
B1000C and C5000D apply to Class 1 explosives. The limit refers to the net explosive mass per transport unit.
Examples from Table A
| UN | Goods and code | What's closed |
|---|---|---|
| 1203 | petrol, (D/E) | tanker: tunnels D and E; drums and cans: E only |
| 1202 | diesel, (D/E) | same as petrol |
| 1978 | propane, (B/D) | tank: B, C, D and E; cylinders: D and E |
| 1005 | anhydrous ammonia, (C/D) | tank: C, D and E; cylinders: D and E |
| 1830 | sulphuric acid, (E) | tunnel E, however it's carried |
| 3082 | environmentally hazardous substance, liquid, (-) | no tunnel |
Example: you're carrying petrol in drums (D/E) and propane in cylinders (B/D), both above the 1.1.3.6 threshold. The stricter code applies to the whole load. In packages, petrol only closes tunnel E, but propane closes D and E. So you can't use a category D or E tunnel.
When the restrictions don't apply
- Tunnel restrictions apply to transport units that must display orange plates, except for goods coded "(-)" (1.9.5.3.6).
- They don't apply to carriage under 1.1.3, for example below the 1.1.3.6 threshold. Those goods are also ignored when working out the code for the whole load (8.6.3.3).
- The exception to the exception: a unit marked for limited quantities under 3.4.13, usually because it carries more than 8 tonnes of them, may not enter a category E tunnel (1.9.5.3.6, 8.6.4).
How tunnels are signed
ADR refers to the signs of the Vienna Convention: sign C, 3h bans vehicles carrying dangerous goods, and signs D, 10a, 10b and 10c direct them along a set route. Below the sign is an extra panel with the letter B, C, D or E. No sign means no restriction (1.9.5.3.2, 1.9.5.3.5). The signs are placed where you can still choose another route (1.9.5.3.4).
Countries publish their restrictions and notify the UNECE secretariat, which makes them public (1.9.5.3.7). Before a trip abroad, check the tunnel categories on your route.
Practise it now
Tunnel codes are a favourite exam topic, because the part before and after the slash is easy to mix up. Our free test explains every answer with the paragraph number. The full syllabus is in the app.
Sources
ADR 2025 (UNECE English text): 1.9.5.1 to 1.9.5.3.7, 5.4.1.1.1 (k), 8.6.3.1 to 8.6.3.3, the table in 8.6.4 and column (15) of Table A in Chapter 3.2. This guide explains the basics. On the road, the wording of ADR and the signs at each tunnel apply.
Updated: 2 October 2026