A model to predict fatigue degraded performance

Maintaining alertness has always been a critical problem for personnel on shift work supporting around the clock operations. Yet vigilance on duty is increasingly threatened by a reliance on sophisticated electronic systems with the attendant increase in the cognitive workload, by a greater reliance on protracted, continuous operations, particularly at night, and by the current emphasis on reduced staffing. An empirically based mathematical algorithm was developed for a tool that can be used to manage fatigue on duty. The algorithm estimates fatigue resulting from extended duty days and fragmented or reduced sleep. It was validated by predicting the observed outcome from a separate study of performance degradation by fatigue (r=0.87; p<0.02). The algorithm would be useful in many human system integration problems such as predicting which crew duty schedules would produce the least fatigue. An example is described comparing shift schedules during two weeks of maritime activity.