Maritime Autonomous Surface Ship (Service)

A maritime autonomous surface ship (MASS) service operates vessels with reduced or no crew, ranging from remotely supervised harbor ferries to fully autonomous workboats. The IMO defines four degrees of autonomy, from a crewed ship with decision support (Degree 1) to a fully autonomous ship that makes decisions itself (Degree 4), and is developing a non-mandatory MASS Code targeted for adoption in 2026, with a mandatory Code targeted to enter force on 1 January 2032. Until then, trials run under the IMO interim MASS guidelines (MSC.1/Circ.1604, 2019) and flag-state approval, with COLREGs application still under review.