ADR special provision 666
Vehicles and battery-powered equipment carried as a load, with their operating dangerous goods, escape the rest of ADR if valves are closed etc.
Vehicles and battery-powered equipment under special provision 388 carried as cargo, along with dangerous goods needed for their operation, are exempt from the rest of ADR on conditions. Liquid-fuel valves between engine or equipment and tank are closed unless the equipment must stay operational, and vehicles are loaded upright and secured where appropriate. For gaseous fuels the tank-to-engine valve is closed and the electrical contact open, with the same exception. Metal hydride storage systems need approval of the country of manufacture (recognised by an ADR party if that country is not one). The valve rules do not apply to vehicles empty of fuel. Fully enclosed vehicles that cannot be readily identified are subject to Chapter 5.2 marking and labelling. Sodium ion battery vehicles may alternatively use special provision 404.
| Value | Applies when |
|---|---|
| 2 bar | maximum gaseous fuel tank pressure for a vehicle to count as empty of gaseous fuel |
Conditions
- (a) Liquid fuels: valves between engine/equipment and fuel tank closed unless operation is essential; vehicles upright and secured where appropriate.
- (b) Gaseous fuels: tank-to-engine valve closed and electric contact open unless operation is essential.
- (c) Metal hydride storage systems need approval from the manufacturing country's competent authority, recognised by an ADR contracting party where that country is outside ADR.
- (d) (a) and (b) do not apply to vehicles empty of liquid or gaseous fuel. Empty of liquid fuel: tank drained and vehicle inoperable for lack of fuel (lines, filters, injectors need not be purged). Empty of gaseous fuel: no liquid in liquefied-gas tanks, pressure not above 2 bar, shut-off valve closed and secured.
- (e) Vehicles fully enclosed so they cannot be readily identified are subject to Chapter 5.2 marking and labelling.
Note. Text continues onto page 655.
Refers to: special provision 388; special provision 404.
Carried by 5 Table A entries
UN 3166 · UN 3171 · UN 3556 · UN 3557 · UN 3558
Source: ADR 2025 (ECE/TRANS/352), Volume I, section 3.3.1, special provision 666, page 654.
Paraphrase in FreightUtils' own words, not the official text. Not yet reviewed.
ADR 2027 amendments (accepted, applying from 1 January 2027) are not yet reflected on this page.