Managing 24/7

Accident Investigation –

Is there a Daytime Bias in your Operation?


Companies collect reams of data about accidents, incidents and injuries, partly in order to meet regulatory requirements. While data collection is a good practice, it’s important to recognize that proper analysis of that data is the only way to expose problem areas. Does your 24-hour operation know what to look for?

Frequently, data on injuries to shiftworkers are combined with data from employees who work only the day shift. Even traditional 24/7 operations, such as steel mills and power stations, have employees and parts of the business that do not run into the evening and night hours. Failure to separate these groups can lead to a dilution effect that can hide an increased accident/injury risk among a certain employee population. Likewise, if accidents aren’t filtered by time of day, the resulting data can mask peak accident risk times.

Analyzing Accidents by Time of Day

At first glance, analyzing injuries by time of day may seem straightforward: group injury data into one-hour time blocks and produce a bar chart of accident frequency. Unfortunately, it’s not usually that simple, as day and night work are often different.

For example, fewer employees may be working at night; there may be fewer supervisors or some areas of the operation may shut down (in a steel mill, all but the furnaces and one or two lines may cease production; in a hospital, the operations suites may shut down, but there may be an increase in the accident and emergency workload). To calculate injury risk (not frequency), the number of injuries per hour must be divided by the number of people working in that hour.

Accident Investigation: Day-Centric?

Unfortunately, as it is likely that most health, safety, and environment managers work during the day, the injuries that are most frequent in daytime hours may be the ones that receive the most attention.

Furthermore, even when the same type of injuries occur both during the day and night shift, such as falls-on-the-same-level, conducting the investigation only during the day can lead to inaccurate findings. After all, there can be causal factors that led to the fall on the night shift that are not present during the day shift.

For example, an investigation on nighttime falls-on-the-same-level injuries might uncover that poor lighting levels and increased employee fatigue played a much larger in causing the nighttime incidents than they did for daytime incidents. Managers that oversee accidents and injuries in 24-hour operations need to be very careful with their methodology to ensure there is not a daytime bias.

How Much Are Fatigue-Related Accidents Costing Your Company 

Fatigue is one the most pervasive causes of human error related accidents, incidents and injuries. Yet:

  • Fatigue is under-reported and under-investigated during accident/incident investigations.
  • Companies rely excessively on subjective evaluations. With no simple test (e.g. blood, urine, breathalyzer) to determine fatigue, the data is often inaccurate.

To help companies have a reliable and objective tool to determine the true cost of fatigue, CIRCADIAN has developed FACTS™  - Fatigue Accident/Incident Causation Testing System. This web-based system will let you know the probability of whether a person was or was not impaired by fatigue at the time of an accident or incident.


  • Objective - Creates a standard for investigating all incidents, accidents and near misses.
  • Scientifically validated - FACTS probability judgments correlate 86% with the judgments of expert human panels.
  • Easy to use – No training required. Features a simple drop-down menu for collecting the incident data as part of the normal accident reporting process
  • Fatigue Risk Management System Tool - In a data-driven FRMS, FACTS allows an organization to assess, benchmark and measure the impact of their FRMS initiatives in terms of reduced costs, risks and liabilities.

Sign-up for a free trial and learn more about FACTS at:

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Have a Question? Need Help?

For over 30 years, CIRCADIAN has been helping shiftwork operations around the world.  Feel free to contact us by clicking here.


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Stoneham, MA, 02180, USA