Assessing Fatigue-Related Impairment Using the Druid® Impairment App

For nearly a decade, the Highland Park, Texas, Department of Public Safety (HPDPS) had been concerned about the demanding schedule required of their officers.


Their 24/48 schedule was typical of many public safety departments, with 24 hours on duty followed by 48 hours off duty. Plus, officers rotated every eight hours between police, fire, and EMS duties. In May 2021 they decided to do something about it. HPDPS embarked on an experimental 48/96 schedule to give the officers more time to sleep between shifts and during shifts when they were on fire or EMS duty. The result led to a schedule change that has the department “reaping the benefit for years and years” according to Wayne Kilmer, Assistant Director of Public Safety.


Fatigue is a major problem for workers in safety-sensitive jobs. OSHA cites that irregular and extended shifts are common among healthcare providers, transportation workers, first responders, firefighters, police officers, military personnel, construction workers, oil field workers, service and hospitality workers and many others – “with accident and injury rates 30% greater during night shifts when compared to day shifts and working 12 hours per day has a 37% increased risk of injury.”


To compare the effect of the schedule change, HPDPS deployed the Druid app and the Druid Enterprise system. The goal was to assess officers’ fitness for duty at both the beginning and end of their shifts under both schedules.


The fatigue study was conducted in two phases. In Phase 1, previously reported a year ago, Impairment Science, Inc. (ISI) assessed the 24/48 schedule over a six-week period with 42 officers participating. A subset of this group took part in the 48/96 experimental schedule. The positive outcome led to rolling


out the 48/96 schedule the following spring with 36 officers participating over another six-week period.


The findings showed that the average start-of-shift scores during Phase 2 were significantly lower than the Phase 1, with a decrease (5.6 points). The decrease in the average end-of-shift scores during Phase 2 were also highly significant (4.6 points). The results of the study appear in a White Paper recently made available on the ISI website.


These findings confirm what the officers reported in HPDPS qualitative surveys. With the 48/96 schedule, 67% reported being “satisfied” or “very satisfied” with their sleep, compared to only 16% when the 24/48 schedule was used.


The HPDPS leadership team’s willingness to experiment with optional scheduling policies and procedures is exemplary. It also demonstrates the usefulness of the Druid app to monitor officers on a regular basis to inform both day-to-day and longer-term personnel decisions. Kilmer added “Your assistance and professionalism in helping us answer this question have paid dividends for our department".



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