MASS Degree 4

The highest IMO MASS degree of autonomy: a fully autonomous ship whose operating system can make decisions and determine actions by itself, without a human operator in the loop. No crew is aboard and no remote operator controls it during normal operation, unlike Degree 3 (remote control, no crew aboard). Degree 4 is the most demanding case for the IMO MASS Code framework, which is non-mandatory from 2026 with mandatory entry into force targeted for 1 January 2032.