Fault management in supervisory control: the effect of false alarms and support

Automation has changed the role of human operators from direct manual control to supervision. Their main task is to monitor whether system performance remains within pre-specified ranges and intervention is only required in unusual situations. One of the consequences is a loss of situation awareness, which significantly affects performance in abnormal, time-critical situation. The present study reports two experiments, both dealing with fault management in a maritime supervisory control task. The first experiment investigated to what extent false alarms would affect performance and diagnosis behaviour when multiple disturbances occurred. Thirty-nine students from maritime curricula diagnosed disturbances that could either be real or turn out to be a false alarm. The presence of false alarms not only affected the rate with which the subsystems under control were sampled, but it also increased problem-solving time. One of the reasons for suboptimal performance in dealing with fault propagation was tunnel vision: participants had a tendency to deal with disturbances sequentially. In the second experiment the effect of support on performance and diagnosis behaviour was investigated. Two types of support were distinguished: interactive support requiring participants to provide the symptom values and automatic support that directly provided the correct action. Thirty students from maritime curricula diagnosed disturbances with the help of either the interactive or the non-interactive support tool. The results indicated that even though both support tools gave the same advice on how to act, more incorrect actions were taken in the non-interactive support condition. Even though no differences in performance were found after the tool had been removed, it was shown that participants who were used to interactive support used a more structured problem-solving strategy than participants used to the non-interactive support. Consequences for system design are discussed