Fatigue Risk Calculator: Folkard-Lombardi Scoring with Regulatory Frameworks

How It Works

1. Enter Shift Pattern

   Input the start time, end time, and duration for each shift in the rotation. Include day shifts, night shifts, and any overtime extensions. The model evaluates each shift individually and cumulatively.

2. Specify Rest Periods

   Enter the hours of rest between consecutive shifts. Short rest periods (under 11 hours) significantly increase fatigue scores. The calculator flags rest periods that violate regulatory minimums.

3. Set Consecutive Work Days

   Enter the number of consecutive days worked before a rest break. Extended runs of 7+ consecutive days compound fatigue even when individual shifts are within normal length.

4. Select Regulatory Framework

   Choose the applicable standard: API RP 755 for refineries and chemical plants, NRC for nuclear facilities, FMCSA for commercial drivers, or EU WTD for European operations. The calculator checks your schedule against that framework's specific limits.

5. Review Fatigue Score and BAC Equivalence

   See the Folkard-Lombardi fatigue index for each shift and the cumulative score across the rotation. The BAC equivalence translates the fatigue level into impairment terms that are immediately understandable.

6. Identify Violations and Recommendations

   The calculator flags any shifts or rest periods that violate the selected regulatory framework and suggests modifications to reduce fatigue risk.

Built For

• Refinery safety managers evaluating whether a proposed shift schedule complies with API RP 755 fatigue management requirements
• Nuclear plant schedulers verifying that operator work hours stay within NRC 10 CFR 26 limits during outage overtime
• Fleet safety directors checking that driver schedules comply with FMCSA hours-of-service rules and rest requirements
• HSE professionals presenting fatigue risk data to operations managers using BAC equivalence to communicate the severity
• Plant managers comparing the fatigue risk of 8-hour vs 12-hour rotation schedules before making a permanent change
• Incident investigators evaluating whether worker fatigue was a contributing factor in a workplace accident
• Union safety committees reviewing proposed schedule changes for fatigue risk before agreeing to new rotation patterns

Features & Capabilities

Folkard-Lombardi Fatigue Model

Quantifies fatigue based on shift duration, time of day (circadian factors), cumulative hours, and rest between shifts. Produces a numerical fatigue index score for each shift and the overall rotation.

4 Regulatory Frameworks

Checks schedules against API RP 755, NRC 10 CFR 26, FMCSA HOS, and EU Working Time Directive. Flags violations and shows which specific rule is exceeded.

BAC Equivalence Display

Translates fatigue scores into blood alcohol concentration equivalence based on published research. Makes fatigue risk immediately understandable to non-technical audiences.

Shift-by-Shift Breakdown

Shows the fatigue score for each individual shift in the rotation so you can identify the highest-risk shifts and target schedule modifications.

Rest Period Analysis

Evaluates rest time between shifts against regulatory minimums and fatigue recovery thresholds. Short rest periods are the most common cause of cumulative fatigue buildup.

Assumptions

• Folkard-Lombardi fatigue scoring model accounts for shift duration, time of day (circadian factors), cumulative hours, and rest between shifts
• BAC equivalence based on Dawson and Reid (1997): 17 hours awake equals approximately 0.05% BAC, 24 hours awake equals approximately 0.10% BAC
• API RP 755 limits: maximum 16 hours in 24 hours, 36 hours in 48 hours, minimum 8 hours rest between shifts, maximum 7 consecutive night shifts
• NRC 10 CFR 26 Subpart I limits: minimum 10-hour break between shifts, maximum 16-hour shift length, 72-hour weekly average limit
• FMCSA HOS: 11-hour driving limit, 14-hour on-duty window, 10 consecutive hours off duty required, 60/70-hour weekly limits
• EU Working Time Directive: 48-hour maximum average work week, minimum 11 consecutive hours rest per 24-hour period, minimum 24-hour weekly rest
• Circadian low point assumed between 02:00 and 06:00 — shifts spanning this window receive higher fatigue scores

Limitations

• Biomathematical models produce population-average estimates — individual fatigue tolerance varies significantly due to age, health, sleep quality, and chronotype
• Does not measure actual sleep obtained — assumes workers achieve typical sleep duration during off-duty periods
• Commute time is not included in the fatigue model but reduces available sleep opportunity, especially for workers with long commutes
• Does not account for sleep disorders (obstructive sleep apnea, insomnia) which dramatically increase fatigue risk independent of schedule design
• Moonlighting or second-job hours are not captured unless manually entered as additional shift entries
• Regulatory framework checks verify schedule parameters only — they do not assess the full scope of a fatigue risk management system (FRMS)
• BAC equivalence is a communication heuristic, not a precise physiological measurement — actual impairment varies by individual and task complexity

References

• API Recommended Practice 755 — Fatigue Risk Management Systems for Personnel in the Refining and Petrochemical Industries (1st Edition, 2010)
• NRC 10 CFR 26 Subpart I — Managing Fatigue (work hour controls for nuclear power plant personnel)
• FMCSA 49 CFR 395 — Hours of Service of Drivers (commercial motor vehicle driver fatigue regulations)
• EU Directive 2003/88/EC — Working Time Directive (maximum weekly hours, minimum rest periods)
• Dawson, D. and Reid, K. (1997) — Fatigue, Alcohol and Performance Impairment, Nature 388:235
• Folkard, S. and Lombardi, D.A. (2006) — Modeling the Impact of the Components of Long Work Hours on Injuries and Accidents, American Journal of Industrial Medicine 49:953-963
• ICAO Doc 9966 — Manual for the Oversight of Fatigue Management Approaches (biomathematical model validation criteria)

Frequently Asked Questions