Agreement M 371: Spain allows multiple trailers in dangerous goods transport

Key data

Dangerous goods transport companies by road have had a new operational tool since October 14, 2026: the Multilateral Agreement M 371, published in the BOE on November 10, 2026, allows a transport unit to circulate with more than one trailer, something that the general ADR regulations limited to just one.

This is not a total liberalization. The agreement establishes concrete technical conditions, express prohibitions, and differentiated requirements depending on the type of goods transported. Companies that want to take advantage of this flexibility must know exactly what is allowed and what is not.

What does this regulation establish?

The ADR (European Agreement concerning the International Carriage of Dangerous Goods by Road) limited until now to a single trailer the dangerous goods transport units. Multilateral Agreement M 371 introduces an exception to that general rule, allowing combinations with several trailers under specific conditions.

The conditions and restrictions of the agreement are as follows:

The agreement falls within the mechanism of section 1.5.1 of Annex A of the ADR, which allows signatory countries to agree on temporary exceptions to the general rule through multilateral agreements. Its validity is limited: from October 14, 2026 to December 16, 2031.

Economic and operational impact

For transport companies, the possibility of combining several trailers in the same unit can translate into a significant reduction in operating costs: fewer trips to move the same cargo volume, better utilization of tractor capacity, and route optimization.

However, the operational gain comes with additional responsibilities:

• Regulatory verification by transit country: each signatory country may have different national requirements. Operating on international routes requires reviewing the legislation of each state through which the unit passes.
• Prohibition of dual central axle trailer: companies operating with this type of configuration must expressly rule it out for dangerous goods.
• Additional technical requirements for explosives: if the semi-trailer transports explosives, the tractor vehicle must be approved under EX/II or EX/III standards, which may involve fleet investment or review of current approval.
• Limited validity until 2031: fleet investment decisions must consider that the agreement may not be renewed or may be revoked in advance by a signatory country.

Who does it affect?

• Road transport companies operating with dangerous goods classified under the ADR.
• Logistics operators managing national and international routes with dangerous goods.
• Companies transporting explosives in semi-trailers that need to verify EX/II or EX/III approval of their tractors.
• Fleet managers and compliance officers in transport companies.
• Transport advisors and consultants working with dangerous goods sector clients.
• Companies with operations in ADR signatory countries of Agreement M 371 that conduct international transits.

Practical example

A Spanish transport company operates regular routes with dangerous goods between Madrid and Lyon (France). Until October 13, 2026, its transport unit could only incorporate one trailer under the general ADR regulations.

From October 14, 2026, thanks to Agreement M 371, that same company could configure its unit with more than one trailer, provided that:

• The combination does not include two central axle trailers (expressly prohibited combination).
• National requirements of both Spain and France (transit and destination country) are met, given that both must be signatories to the agreement.
• All technical provisions of the ADR applicable to the transported goods are respected.

If that company also transports explosives in a semi-trailer, it must verify that its tractor vehicle has EX/II or EX/III approval before configuring the combination. If the current tractor does not meet those requirements, it will need to adapt the fleet or assign an approved vehicle to that route.

What should companies do now?

1. Review whether Agreement M 371 applies to your routes: verify that the transit and destination countries are signatories to the agreement. Each country's accession is a prerequisite for being able to benefit from the exception.
2. Audit your fleet configuration: identify which trailer combinations you currently use and which you want to implement. Rule out any combination with two central axle trailers, which is expressly prohibited.
3. Verify EX/II or EX/III approval if you transport explosives: if any of your routes include explosives in a semi-trailer, check that the tractor vehicle meets EX/II or EX/III requirements. If not, plan the adaptation before operating with the new configuration.
4. Consult the national regulations of each transit country: the agreement requires compliance with the national legislation of each state through which the unit passes. This is especially relevant on international routes with multiple transit countries.
5. Plan with a 2031 horizon: the agreement is valid until December 16, 2031 and can be revoked in advance. Fleet investment decisions must consider this expiration risk.
6. Document compliance: maintain updated records of approvals, fleet configurations, and regulatory verifications by country, to be prepared for a possible inspection.

Official source

Consult complete regulations in official source

Notice: This article is for informational purposes only and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-23528