IBR President Dr. Steven Hursh invented the SAFTE™ (Sleep, Activity, Fatigue, and Task Effectiveness) model of human fatigue and circadian variation, through efforts sponsored by the US Department of Transportation (DOT) and the US Department of Defense (DOD), and co-developed the FAST (Fatigue Avoidance Scheduling Tool) application used to anticipate and avoid fatigue in transportation operations.

SAFTE is a computerized model that predicts changes in cognitive performance based on the sleep/wake schedule and the body’s internal clock. It contains: a circadian process, a circadian sleep propensity process, a sleep fragmentation process, and a phase adjusting feature for time zone changes. The patented SAFTE model has received a broad scientific review and the DOD considers it the most complete, accurate, and operationally practical model currently available to aid operator scheduling (Hursh, Balkin, Miller, and Eddy, 2004).

The US DOT has also undertaken a multi-phased project to validate and calibrate the model for avoiding excessive fatigue in transportation operations. The model was subjected to an independent review against a range of scenarios, along with five other models from around the world, and was found to have the least error overall of any current model (Hursh, Redmond, Johnson, Thorne, Belenky, Balkin, Storm, Miller, and Eddy, 2004).

Recently, the Federal Railroad Administration completed an extensive test of the model against two years of railroad accident data and work histories prior to those accidents (Hursh et al., 2006; Dean, et al. 2007).

The study found that model predictions of decreased operator effectiveness were reliably related to increased human factors accident risk (r = – 0.93, p < 0.01).