The International Code for Safety for Maritime Autonomous Surface Ships, known as the MASS Code, comes into force this July 1 voluntarily, following its adoption by the International Maritime Organization (IMO) during the 111th session of the Maritime Safety Committee (MSC 111) held in London on May 22. This is the first global regulation that sets a framework of requirements for the design, construction, operation, and certification of autonomous and remotely controlled commercial ships.
The aim of the code is for these vessels to meet safety and environmental protection standards equivalent to those of conventional ships. Its application is currently limited to large cargo ships dedicated to international trade. The IMO has postponed extending the code to passenger ships, a decision that responds to the greater complexity of safety and liability considerations in autonomous operations with passengers on board, and has indicated that it will evaluate that extension as experience accumulates during the voluntary phase.
The entry into force on this July 1 marks the beginning of what the IMO calls the 'experience-gathering phase,' the formal framework of which will be developed in MSC 112, scheduled for December 2026. During this period, which will last at least two years, member states will be able to test the practical application of the code before it becomes mandatory under the SOLAS Convention, a step that could occur starting from 2028. The adoption of the mandatory version is planned for July 1, 2030, with effective entry into force through amendments to the SOLAS Convention on January 1, 2032, through what is shaping up to be a future Chapter XVI of said convention.
Spain has actively participated in the drafting process of the code over the past eight years, a development that has run parallel to the technological evolution of autonomous ships. The Spanish delegation at MSC 111 was composed of Víctor Jiménez, president of the IMO Council and permanent representative of Spain to the organization; Andrés Galván, also a member of the Spanish Permanent Representation; and Hernán del Frade, coordinator of the national working group on autonomous ships and advisor on safety and environment of the General Directorate of Merchant Marine (DGMM).
The MASS Code defines a maritime autonomous surface ship as one capable of operating with varying degrees of independence from human intervention and outlines four levels of autonomy. At level one, the crew remains on board with the support of automated decision-aid processes. At level two, the ship is controlled from a remote location but maintains a crew on board available to take control. Level three corresponds to remote control without crew on board. Level four is fully autonomous operation, where the ship's own system determines actions without direct human intervention.
The regulatory framework is goal-based, lacking the prescriptive specificity of other SOLAS Convention regulations. It incorporates by reference the collision avoidance rules of the COLREG Convention and adds a situational awareness requirement that obliges the autonomous navigation system to continuously monitor all necessary information for safe navigation. More specific standards, such as the capability to evaluate sound signals or VHF calls, are not part of the code at the moment, as most current autonomous navigation systems cannot perform them.
The text includes an extensive list of equipment requirements exclusive to unmanned ships, which must be designed differently to ensure safety and response to emergencies in what the code calls 'reasonably foreseeable degraded states.' This implies differentiated standards in structure, subdivision, stability, and watertight integrity, fire protection, lifesaving devices, search and rescue, cargo handling, towing and mooring, machinery installations, and electrical installations. Anchor winches, for example, must operate autonomously or remotely during an emergency without crew removing the restraints, and emergency towing systems must be able to establish connection without crew handling the lines under adverse sea conditions.
The code maintains the figure of a designated captain, either on board or from a Remote Operations Center (ROC) on shore, with actual capability for intervention. The ROC itself will be subject to certification by the flag state administration of the ship they operate, introducing a formal accountability structure for shore-based operation. The code also covers matters such as system design, software principles, connectivity, alert management, fire protection, search and rescue, machinery and electrical installations, recognitions and certification, and anchoring and mooring.
According to the DGMM's technical presentation on the regulatory process, the origin of this regulation dates back to 1964, when the IMO first addressed the autonomy of ships under the UMS concept. The debate was revived in 2017 during MSC 97 when the organization highlighted the need to verify whether autonomous ships would comply with their conventions. Between 2018 and 2019, an exploratory regulatory study was conducted, the conclusions of which led in 2021 to the decision to develop a specific instrument, developed since then by an ad hoc working group.
Shipyards, design offices, classification societies, and insurers now have a reference framework against which to assess technological readiness for automation and remote operation. A ship commissioned in 2026 can remain in commercial service well into the 2050s, so the regulatory certainty provided by the code has direct consequences for investment decisions in the sector.
Manned conventional ships will continue to dominate commercial operations in the foreseeable future. However, the autonomous ship already has a legal identity within the international regulatory system and a defined roadmap towards its mandatory regulation, while open questions persist such as the applicable jurisdiction over remote operations centers or the availability of sufficient operational MASS ships to provide data for the testing phase.
