Figure 1.

One-step and 2-step biomathematical models of human fatigue and performance. Continuous lines represent the passing of known values, while broken lines, the passing of estimated values. One-step models, represented on the left-side panel, generate outputs via predictive algorithms that require input of known work-rest and sleep-wake times. Two-step models, represented on the right-side panel, include intervening algorithms to estimate sleep-wake times based solely on known or planned work-rest times.