Chapter 3 - Manual Fatigue Audit System

Overview

For organizations with relatively simple schedules or that may not want to invest in software, manual calculations can also be performed to generate scores that provide an indication of fatigue likelihood. A fatigue likelihood scoring matrix uses five scheduling parameters to predict sleep opportunity. These can be used to estimate the degree of work-related fatigue produced by a given schedule:

  1. Total number of hours worked in a seven-day period. Not surprisingly, as total hours worked increases, sleep opportunity decreases.

  2. Maximum length of an individual shift. As the length of a given shift increases, the subsequent sleep opportunity decreases.

  3. Minimum length of a short break. A short break is defined as a single sleep opportunity between work periods. It is typically shorter than 32 hours. Not surprisingly, as the break between shifts decreases, so does sleep opportunity.

  4. Total number of hours worked between 9 p.m. and 9 a.m. in a seven-day period. This parameter takes into account late finishes, early starts, and night work. All of these will reduce night sleep opportunity and result in a significant reduction in total sleep opportunity.

  5. Frequency of long breaks. A long break is defined as a period of two night sleeps with a non-working day in between. Long breaks typically provide a significant opportunity to recover from sleep loss accumulated over a sequence of work periods. A schedule can be scored on each of the five parameters using the following table.

Fatigue Likelihood Scoring Matrix for Work Schedules

Score 0 1 2 4 8
a) Total hours per 7 days less than or equal to36 hours 36.1 – 43.9 44 – 47.9 48 – 54.9 55+
b) Maximum shift duration less than or equal to8 hours 8.1 – 9.9 10 – 11.9 12 – 13.9 14+
c) Minimum short break duration greater than or equal to16 hours 15.9 – 13 12.9 – 10 9.9 – 8 less than or equal to8
d) Maximum night work per 7 days 0 hours 0.1 – 8 8.1 – 16 16.1 – 24 24+
e) Long break frequency greater than or equal to1 in 7 days less than or equal to1 in 7 days less than or equal to1 in 14 days less than or equal to1 in 21 days less than or equal to1 in 28 days

The points for each parameter are added up to provide a score between 0 and 40 that indicates the degree of sleep opportunity provided by the schedule. Schedules with a lower score offer a greater sleep opportunity. The figure below shows several schedules scored using this approach.

Fatigue Likelihood Score

 Fatigue Likelihood Score

Examples of different schedules scored using the Fatigue Likelihood Scoring Matrix

Example 1

Day Description Start Finish
1 Morning 0500 1400
2 Morning 0500 1400
3 Afternoon 1330 2230
4 Afternoon 1330 2230
5 Off 0000 0000
6 Night 2200 0600
7 Night 2200 0600

Using the five parameters, this schedule would be scored as follows:

  1. The total number of hours worked during the seven-day work period is 52 (4 points).

  2. The maximum shift duration is 9 hours (1 point).

  3. The minimum time off between shifts (short break) is 15 hours (1 point).

  4. The total hours of night work scheduled for the seven-day period is 23. This includes 4 hours on each of the morning shifts due to the early shift starts, 1.5 hours on each of the afternoon shifts due the late finish, and 8 hours on each of the night shifts (4 points).

  5. The long break frequency is 1 day within the 7 days of the schedule before the individual starts the night shift on Day 6 (0 points).

The total score for the above schedule is 10 points.

Example 2

Day Description Start Finish
1 Day 0600 1400
2 Day 0600 1400
3 Off 0000 0000
4 Afternoon 1400 2300
5 Afternoon 1400 2300
6 Afternoon 1400 2300
7 Night 2300 0600

Using the five parameters, this schedule would be scored as follows:

  1. The total number of hours worked during the seven-day work period is 50 (4 points).

  2. The maximum shift duration is 9 hours (1 point).

  3. The minimum time off between shifts (short break) is 15 hours (1 point).

  4. The total hours of night work scheduled for the seven-day period is 19. The employee works 3 hours on each of the morning shifts due to the early start, 2 hours on each of the afternoon shifts due the late finish, and 7 hours on the night shift (4 points).

  5. The long break frequency is 1 day before the individual starts the afternoon shift on Day 4 (0 points).

Le pointage total de l’horaire ci-dessus est de 10 points.

Summary

Any work schedule can be run through this scoring system. For example:

  • Monday to Friday, 9 a.m. to 5 p.m (40 hours) receives a score of 1

  • Monday to Friday, 3 p.m. to 11 p.m. (40 hours) receives a score of 3

  • 4 days on – 4 days off (2 days from 6 a.m. to 6 p.m., 2 days from 6 p.m. to 6 a.m., for a total of 48 hours) receives a score of 14

  • Monday to Friday, 6 a.m. to 6 p.m. (60 hours) receives a score of 16

  • 7 night shifts of 12 hours, 9 p.m. to 9 a.m. (84 hours), followed by 7 days off receives a score of 22

Based on a company’s risk assessments, managers can consider whether existing work schedules produce acceptable levels of fatigue-related risk.

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