Fatigue risk index (FRI)
A fatigue risk index (FRI) is a scoring approach used to estimate fatigue exposure associated with a roster or shift pattern. It typically considers factors such as shift timing, duration, rest between shifts, and consecutive working days.
FRI methods are used in some UK industries — particularly transport — to support roster review and dialogue between planners, safety teams, and workforce representatives.
What FRI can help with
Section titled “What FRI can help with”Used appropriately, an FRI can:
- Provide a consistent basis for comparing roster options
- Highlight shifts or sequences with elevated fatigue exposure
- Support evidence-led discussions during roster design or change
- Complement — not replace — wider fatigue risk assessment
Limitations
Section titled “Limitations”FRI scores are models, not measurements of an individual’s actual alertness. Important caveats include:
- Individual sleep, health, and lifestyle vary significantly
- Models may not capture local operational factors (commute, workload spikes, disruption)
- A low score does not guarantee safety; a high score does not automatically mean a shift must be cancelled
- Different FRI methodologies exist and may produce different results
Any FRI output should be interpreted by competent persons and considered alongside operational experience.
Typical inputs
Section titled “Typical inputs”Depending on the methodology, inputs may include:
- Shift start and end times
- Shift length and type (day, night, split)
- Rest period before and after shifts
- Number of consecutive shifts
- Break provisions within shifts
Related pages
Section titled “Related pages”Further research
Section titled “Further research”Specific FRI methodologies (including rail-sector approaches) and academic validation will be documented with source references in a future update.