Fatigue is a major human factors issue in aviation safety. The Fatigue Avoidance Scheduling Tool (FAST) was developed by the United States Air Force in 2000–2001 to address the problem of aircrew fatigue in aircrew flight scheduling. FAST is a Windows program that allows scientists, planners and schedulers to quantify the effects of various work-rest schedules on human performance. It allows work and sleep data entry in graphic, symbolic (grid) and text formats. The graphic input-output display shows cognitive performance effectiveness (y axis) as a function of time (x axis). An upper green area on the graph ends at the time for normal sleep, 90% effectiveness. The goal of the planner or scheduler is to keep performance effectiveness at or above 90% by manipulating the timing and lengths of work and rest periods. A work schedule is entered as red bands on the time line. Sleep periods are entered as blue bands across the time line, below the red bands.
The calculated performance effectiveness represents composite human performance on a number of cognitive tasks, scaled from zero to 100%. The oscillating line in the graph represents expected group average performance on these tasks as determined by time of day, circadian rhythm, time spent awake, and amount of sleep, and various confidence limits around the average may be displayed. The graphic display may be cut and pasted into reports and briefing slides. Cognitive effectiveness estimates for work periods of any length may also be cut and pasted in tabular format.
History
FAST was developed under Phase 1 and 2 Small Business Innovation Research (SBIR) contract awards from the US Air Force Research Laboratory (AFRL), Human Effectiveness Directorate, to NTI, Inc. (Dr. Douglas R. Eddy, Principal Investigator) with Science Applications International Corporation as a subcontractor (Dr. Steven R. Hursh, Modeler). Fatigue predictions in FAST are derived from the Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) simulation invented by Dr. Hursh, currently the President of the Institutes for Behavior Resources and Adjunct Professor of Behavioral Biology, Johns Hopkins University School of Medicine.
The SAFTE simulation integrates quantitative information about (1) the circadian rhythm in metabolic rate; (2) cognitive performance recovery rates associated with sleep, and cognitive performance decay rates associated with wakefulness; and (3) cognitive performance effects associated with sleep inertia to produce a 3-process model of human cognitive effectiveness. The SAFTE model has been under development by Dr. Hursh for more than a decade. In the general architecture of the SAFTE model, a circadian process influences both cognitive effectiveness and sleep regulation. Sleep regulation is dependent upon hours of sleep, hours of wakefulness, current sleep debt, the circadian process and sleep fragmentation (awakenings during a sleep period). Cognitive effectiveness is dependent upon the current balance of the sleep regulation process, the circadian process, and sleep inertia.
The SAFTE simulation has received a broad scientific review and the DoD considers it a complete, accurate, and operationally practical model to aid operator scheduling. The SAFTE simulation's software implementation and applicabilities have since been validated in aviation and railroad work environments.
During the Phase 2 effort, the model was refined with findings from AF research and other studies providing a blood alcohol index, lapse index, sleep timing algorithm, and interface features (performance variation percentiles, mission timeline, grid input, and fatigue factors dashboard, to name a few). FAST provided the military physiologist the first computerized tool that used a homeostatic model for optimizing aviator performance under conditions of limited sleep while minimizing the need for pharmacological aids. Missions could be planned that provided sufficient rest to maintain effective performance and, when normal, nocturnal sleep was impossible, arrange interventions such as naps or pharmacological treatments to maintain performance. The tool was intended to improve flight safety, optimize mission success during sustained operations, and minimize the need for pharmacological aids.