Workload of the steering work on a high-speed vessel.

The higher incidence of accidents occurring on board among the high-speed vessels has motivated this study focusing on the actual operating conditions contributing to the incidence. The working activities and workload of the officers and quartermasters were compared between the conventional and high-speed vessels of regular service ferry, by recording video-pictures and heart rate of the crews during actual navigations. An autopilot equipment was installed in the conventional vessel of over 6000 tons, but not in the high-speed vessel of about 1500 tons. Either on the conventional or high-speed vessel, dominant activities of the officers were lookout and watching radar, which were conducted in standing on the conventional vessel and in sitting on the high-speed vessel. Major works of the quartermasters were lookout and radar watch in standing on the conventional vessel and steering operations with a joystick in sitting on the high-speed vessel. Despite these differences in postural conditions, the mean % heart rate increase in both crews was significantly higher on the high-speed than on the conventional vessel. In the quartermaster, the events requiring steering maneuvers on the high-speed vessel were associated with increase in heart rate. The findings as a whole suggest occurrence of substantial mental strains in the crew on the high-speed vessel. These strains, certainly derived from caring for the safety in the absence of autopilot equipment, must have intensified the workload in the crew. In connection with the workload, the necessity for some fail-safe systems, including the autopilot facilities, and educational systems for techniques of steering high-speed vessels was discussed.