IMO Regulatory Scoping Exercise for MASS (MSC.1/Circ.1638)

emerging Updated: 2026-06-13
mass imo regulatory-scoping-exercise degrees-of-autonomy solas mass-code goal-based-standards maritime-regulation remote-control-centre colreg

IMO Regulatory Scoping Exercise for MASS (MSC.1/Circ.1638)

Status: emerging
Last updated: 2026-06-13
Sources: Msc.1 Circ.1638 Mass Regulatory Scoping Exercise.Pdf
Tags: [mass, imo, regulatory-scoping-exercise, degrees-of-autonomy, solas, mass-code, goal-based-standards, maritime-regulation, remote-control-centre, colreg]

Summary

When ships began to be designed to operate with reduced or no crew, it was unclear whether the existing body of IMO safety and security regulation — written for crewed ships — even applied to them, let alone permitted them. The IMO Maritime Safety Committee ran a regulatory scoping exercise (RSE) to find out, examining each mandatory instrument under its purview against four defined degrees of autonomy. MSC.1/Circ.1638 (2021) reports the result: a definition of MASS and its degrees of autonomy, a two-step method for classifying every provision, a list of cross-cutting gaps and themes (the meaning of "master" and "crew", the remote control centre, and the remote operator's status as a seafarer chief among them), and a recommended way forward. The Committee's central conclusion is that the many issues cutting across instruments would best be addressed not by amending each convention separately but holistically through a new, goal-based instrument — a "MASS Code". The document is the foundational regulatory map for autonomous shipping.

Body

Context

MSC.1/Circ.1638 (IMO, 2021) is the Maritime Safety Committee's report of the regulatory scoping exercise on MASS, approved at MSC 103 (5–14 May 2021) after a process begun at MSC 98 in 2017 (Annex pp. 1–3; PDF pp. 3–5). Its aim was to determine how safe, secure and environmentally sound MASS operations might be addressed in IMO instruments, and its objective was to assess the degree to which the existing framework under the MSC's purview is affected by MASS (Annex p. 3; PDF p. 5). Within this knowledge base it anchors the maritime-regulation and emerging-technologies focus areas, and it provides the regulatory context for the human-element work in Situation Awareness Maritime Accidents and Simultaneous Tasks Maritime Accidents (both concern the crewed bridge whose functions MASS reassigns). It is the maritime-regulatory counterpart to the MASS automation and COLREG analyses held in the artificial-intelligence and remote-operations knowledge bases.

Key Points

MASS is defined by four degrees of autonomy. For the RSE, MASS was defined as "a ship which, to a varying degree, can operate independent of human interaction", organised into four degrees: Degree One, a ship with automated processes and decision support but seafarers on board to operate and control it; Degree Two, a remotely controlled ship with seafarers on board; Degree Three, a remotely controlled ship without seafarers on board; and Degree Four, a fully autonomous ship whose operating system makes decisions and determines actions by itself (Annex pp. 6–7; PDF pp. 8–9). These degrees are descriptive levels rather than a developmental sequence, and each instrument was assessed against all four.

The method was a two-step assessment of every provision. In the first step, volunteering Member States classified each provision of each mandatory instrument by how it bears on MASS: whether it applies and would prevent MASS operations, applies without obstacle, applies but might need amendment or clarification and/or contains gaps (category C), or has no application to MASS (category D) (Annex p. 6; PDF p. 8). In the second step, the most appropriate way of addressing MASS in each instrument was determined — taking account of the human element, technology, and operational factors — by one or more of: (I) equivalences or interpretations provided for by the instruments; (II) amending existing instruments; (III) developing new instruments; or (IV) none of these (Annex p. 6; PDF p. 8). The instrument-by-instrument results occupy Appendix 2, the bulk of the document.

The RSE surfaced cross-cutting gaps, several of them high-priority policy issues. The exercise identified common potential gaps and themes spanning many instruments and SOLAS chapters, including the meaning of the terms master, crew or responsible person; the remote control station/centre; the designation of a remote operator as a seafarer; provisions assuming manual operations or personnel actions on board; watchkeeping; connectivity and cybersecurity; implications for search and rescue; certificates and manuals carried on board; and terminology (Annex pp. 7–8; PDF pp. 9–10). Three were singled out as high-priority issues at the core of introducing MASS safely — the meaning of master/crew/responsible person, the remote control centre, and the remote operator as seafarer — each likely to require a policy decision before individual instruments can be addressed (Annex p. 8; PDF p. 10).

The recommended way forward is a goal-based MASS Code. Because the gaps cut across so many instruments, the Committee concluded they could preferably be addressed holistically through a new instrument — for example a MASS Code — rather than by amending each convention separately, which could create inconsistencies and raise barriers for conventional ships; such an instrument could be made mandatory by amending an existing convention such as SOLAS and could be developed following a goal-based approach in line with the IMO's goal-based standards guidelines (Annex pp. 8–9; PDF pp. 10–11). Interim guidelines were suggested to enable early MASS operation, and agreement on terminology — including re-evaluating the degrees of autonomy and developing a glossary — was identified as a prerequisite policy decision. If instead instruments were to be amended individually, the RSE proposed grouping them into high-, medium- and low-priority sets (Annex pp. 8–9; PDF pp. 10–11).

Conclusion

MSC.1/Circ.1638 concludes the IMO's first systematic test of whether its safety and security regime can accommodate autonomous ships, and finds that while much of the existing framework applies, a substantial set of cross-cutting gaps — above all the human-centred questions of who the "master" and "crew" are when no one is on board and who counts as a seafarer when the operator is ashore — cannot be resolved instrument by instrument. The Committee's recommendation is a single, goal-based MASS instrument made mandatory through SOLAS, preceded by agreement on terminology and the degrees of autonomy. The document does not itself change any regulation; it is a scoping map that frames the subsequent work programme (which led toward a non-mandatory MASS Code). For this knowledge base it is the regulatory backbone against which the technical, operational, and human-factors sources on autonomous shipping are read.

References

International Maritime Organization (2021) MSC.1/Circ.1638: Outcome of the Regulatory Scoping Exercise for the Use of Maritime Autonomous Surface Ships (MASS). London: International Maritime Organization, 3 June 2021. imo2021massrse

Open Questions

  • The RSE recommends a goal-based MASS Code but leaves the choice between a new instrument and amending existing conventions as an open policy decision. Which path the IMO took, and how the degrees of autonomy were re-evaluated afterward, is not in this document and should be tracked with a follow-up source.
  • The three high-priority issues (master/crew/responsible person, remote control centre, remote operator as seafarer) are human-centred but assessed here only at the level of regulatory text. How they map onto the actual cognitive and operational demands of remote/autonomous operation is addressed elsewhere in the corpus, not here.
  • Appendix 2 (the instrument-by-instrument results) is the substantive core but is a large reference table; only its summary themes are compiled here. Specific instrument findings (e.g. for COLREG, STCW, SOLAS chapter V) can be drawn out into dedicated notes if needed.