Ten deck officers with various ranks, including the third officer and captain, participated in the case study. The NASA task load index method was used to measure MWL. The case study was carried out by utilising the scheme on typical cases focusing on the normal navigational situation. Five factors related to MASS operation were defined, in addition to general factors. The provided scheme identifies the factors that affect the MWL of operators and sub-elements of MWL through gap analysis. This research aims to provide a scheme for identifying the relationship between MWL and MASS in the maritime that can be utilised for rulemaking and technological development. On the other hand, MASS may have adverse effects on operators’ mental workload (MWL) and increase safety risks in some cases. Maritime autonomous surface ships (MASS) have been expected to reduce marine accidents by human error of the seafarers. Shipping is an indispensable tool for the sustainable global supply chain, and seafarers play a key role in safe navigation.
