Green light for more than one trailer for dangerous goods until 2031

Road carriers of dangerous goods may operate with transport units that include more than one trailer or semi-trailer under the Multilateral Agreement M 371, in effect since October 14, 2026. The text is published in the Official State Gazette (Boletín Oficial del Estado) no. 280, of November 10, 2026, in section I of general provisions, with the official reference BOE-A-2026-23528. The signature corresponds to the competent authority for the ADR in the Kingdom of Spain.

The agreement is based on paragraph 1.5.1 of Annex A of the ADR, the European Agreement concerning the International Carriage of Dangerous Goods by Road, and expressly repeals section 8.1.1 of that regulation, which limits the transport unit to a single trailer or semi-trailer. It is disseminated by the Ministry of Foreign Affairs, European Union and Cooperation as an administrative international agreement, meaning it does not require parliamentary processing.

This is not the first time Spain has activated this route: the immediate precedent is Multilateral Agreement M342, published in the Official State Gazette of December 20, 2021 (BOE-A-2021-20910) and valid until December 16, 2026, while Multilateral Agreement M 304, disseminated on May 19, 2017 (BOE-A-2017-5561), covered the previous period. The new M 371 extends and expands that framework until 2031.

Conditions for circulating with more than one trailer

The text does not grant a free authorization, but rather establishes six cumulative requirements:

• The transport unit must fully comply with the regulations on vehicle combinations of the country or countries where the operation is carried out.
• If the unit includes a vehicle and a Dolly converter—defined as a trailer designed for the sole purpose of towing a semi-trailer—it must satisfy the requirements of the ADR and be approved accordingly.
• When special provision V2 (2) of paragraph 7.2.4 of the ADR is applicable and explosives are carried in a semi-trailer, the towing vehicle must meet the requirements for EX/II or EX/III vehicles, as appropriate.
• A transport unit may not include two center-axle trailers.
• All other relevant provisions of the ADR must be complied with.

Validity until 2031 and possible revocation

Validity extends until December 16, 2031, but only for transport within the territories of the Contracting Parties to the ADR that have signed the agreement. If any signatory revokes it before that date, the text will remain applicable only in the territories of the Parties that have not revoked it, meaning coverage may be fragmented by country without the agreement lapsing completely.

Who signs it and with what technical backing

The competent authority for the ADR in the Kingdom of Spain is the Director General of Road and Rail Transport, Elena María Atance Herreros, whose department is bound by the interpretation and application of the agreement. The Executive refers the text to the Official State Gazette through the Technical General Secretariat of the Ministry of Foreign Affairs, European Union and Cooperation, whose head, Carmen Burguillo Burgos, signs the document in Madrid on November 3, 2026.

The agreement arrives at a time when the previous multilateral framework was expiring: the M342 lapses on December 16, 2026, barely a month after this publication, so the M 371 avoids a regulatory vacuum for companies already operating with vehicle combinations.

The impact is direct for the dangerous goods transport sector: companies will be able to optimize loads and reduce trips by combining trailers, provided that the combination is approved and complies with the national rules of each country through which the convoy passes. For logistics operators and shippers, the new framework provides five years of legal stability on international routes, although it requires reviewing vehicle configurations, authorizations, and approval documentation before taking advantage of the additional capacity.

Source: Official State Gazette, no. 280, of November 10, 2026, Sec. I. General provisions, page 151505 (official reference: BOE-A-2026-23528).