Tunnel Restrictions and Special Rules for Dangerous Goods Transport
Tunnel categories
ADR defines tunnel categories A to E based on risk. Category A has no restrictions; category E restricts the most dangerous goods. Each tunnel is assigned a category, and each dangerous goods load is assigned a tunnel restriction code in the Dangerous Goods List. The driver must compare the load's tunnel restriction code with the tunnel category. Traps: confusing the tunnel category letter with the restriction code, and assuming all tunnels accept all loads.
Special rules
Beyond tunnels, some routes, bridges, city centres and ports have special restrictions. The driver must plan the route and check national and local rules. Some classes require escort, prior notification, or a specific route. Traps: relying only on ADR and ignoring national route rules, and assuming a low tunnel category means no restriction at all.
Worked rule of thumb
Read the tunnel restriction code from the Dangerous Goods List, then compare it with the tunnel category sign. If the restriction code is not permitted in that category, the route is closed to that load; find another route.