Identifying and Reducing Workforce Fatigue in Rapid Renewal Projects (2014)

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108 A p p e n d i x d This appendix contains work schedule guidance and work practice recommendations for the range of shift schedules commonly encountered in rapid renewal construction. The guidance consists of fatigue models for each basic work- schedule type (Day Shift, Night Shift, Weekend Closure, Switching Shifts, Manager and Designer), typical schedule variations for a few basic types, and both preventive and oper- ational fatigue countermeasures tailored for each work sched- ule type. Included are work start and stop times, likely sleep times, and assumptions made in preparing schedule-based fatigue models. Issues of concern for each schedule type are discussed, including the overall profile of fatigue during the work period; cumulative impacts; and potential counter- measures to apply, including modifications to shift length, days off prior to switching shifts, rest breaks, and so forth. The Fatigue Management Key Points starting on this page provide a brief introduction to the major principles in fatigue management, which are derived from schedule-based fatigue modeling. To determine likely fatigue levels of per- sonnel on a daily and weekly basis, turn to the pages contain- ing the shift type(s) of interest. For the Day and Night schedules, a number of variations are included as well. Sub- sequent pages contain details specific to schedule variations within that basic schedule type. Weekend closure, shift switching, and manager examples use a 50-h week as the “base” schedule, but fatigue profiles, assumptions, and countermea- sures also apply to longer and shorter work weeks within that schedule type. These shift profiles and countermeasures are intended as guidance only; they are meant to provide managers with information to make decisions about specific work assign- ments and for planning overall construction schedules to bal- ance worker fatigue management with project schedule goals. There is no one-size-fits-all solution for a project or for an individual worker. This guidance is intended to assist manag- ers in achieving a balance between project objectives and worker fatigue management. Fatigue Management Key points • Day shifts have substantially lower fatigue levels than night shifts, including peak fatigue (Figure D.1.). • Fatigue accumulates over time if it is not relieved through sufficient sleep. Fatigue is highly likely to accumulate while working night shift (Figure D.1.). • Brief naps at appropriate times in the work period, especially on a night shift, reduce immediate fatigue and its accumula- tion over time (Figure D.1.). • Restricted sleep (sleep lost due to work demands, family demands, social activities, stress, etc.) can affect fatigue for several days and may take more than a single night of good sleep to recover from (Figure D.2.). • The time night shift ends largely determines fatigue lev- els; earlier shift end times reduce peak fatigue during the shift and also slow accumulation of fatigue over time. (Figure D.3.). • Day shifts, if they are very long, can also result in increased peak fatigue and accumulation of fatigue over time—for example, a designer or manager working a high-production schedule of 80 h per week (Figure D.4.). day Shift Schedules Example: 40-h Week (5 days × 8 h per day) Application Standard, non-accelerated construction. Shift Start Time: 7:00 a.m. Shift End Time: 3:30 p.m. Bedtime: 10:00 p.m. Wake Up: 5:30 a.m. Fatigue Risk Management Schedule Guidance and Work Practices

109 Figure D.1. Peak fatigue: 5  10 (50-h week) day shift and night shift with and without naps. Monday Tuesday Wednesday Thursday Friday G re at er Fa tig ue day shift night shift, with naps night shift, no naps Figure D.2. Peak fatigue: day shift with normal sleep (7.5 h per night) and 1 and 2 nights’ restricted sleep (4.5 h). Monday Tuesday Wednesday Thursday Friday G re at er Fa tig ue normal sleep 1 night, 4.5 hours 2 nights, 4.5 hours Figure D.3. Peak fatigue: night shift with various work stop times. Monday Tuesday Wednesday Thursday Friday G re at er Fa tig ue shift end 4:30 am shift end 6:30 am shift end 7:30 am

110 Assumptions • 30-min meal break • 1-h commute • 7.5 h of sleep nightly • 30 min of personal time between waking up and starting work Fatigue Profile Fatigue peaks just after noon, declines toward evening, and then rises sharply before bedtime. (Figure D.5.). Preventive Countermeasures • Maintain consistent sleep and wake times throughout the week. • Maintain similar or identical sleep and wake times on week- end or nonwork days. Operational Countermeasures • Caffeine during day, but no later than 4:00 p.m. • Strategic naps (on-the-job) to reduce impact of restricted sleep. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. Comments • With each of the following conditions there is the poten- tial for fatigue to accumulate over time as sleep duration declines: 44 Shifts that are longer than 10 h (see variations) may lead to reduced sleep durations due to a later arrival time home and the need for additional time for personal activities. Figure D.4. Peak fatigue: high production designer or engineer schedule versus typical day schedule. Monday Tuesday Wednesday Thursday Friday G re at er Fa tig ue standard day shift designer, high production Figure D.5. Fatigue profile: day shift schedules.

111 44 Shifts that begin before 7:00 a.m. may lead to reduced sleep durations because individuals may not be able to compensate for an earlier wake time by going to bed earlier. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to both an earlier wake time and a later arrival time home. day Shift Schedule Variations The same assumptions, fatigue profile, recommended counter- measures, and general comments apply for all day shift variations. 48-h Week (4 days × 10 h per day, 1 day × 8 h per day) Application Accelerated schedules, day shift, with or without use of two- shift construction with nighttime closures and break during evening rush hour. Mon. to Thur. Fri. Shift Start Time: 7:00 a.m. 7:00 a.m. Shift End Time: 5:30 p.m. 3:30 p.m. Bedtime: 10:00 p.m. 10:00 p.m. Wake Up: 5:30 a.m. 5:30 a.m. 50-h Week (5 days × 10 h per day) Application Accelerated schedules, day shift, with or without use of two- shift construction with nighttime closures and break during evening rush hour. Shift Start Time: 7:00 a.m. Shift End Time: 5:30 p.m. Bedtime: 10:00 p.m. Wake Up: 5:30 a.m. 60-h Week (5 days × 12 h per day) Application Accelerated schedules, day shift, with or without use of two- shift construction with nighttime closures and no break for traffic. Shift Start Time: 7:00 a.m. Shift End Time: 7:30 p.m. Bedtime: 10:00 p.m. Wake Up: 5:30 a.m. night Shift Schedules Example: 40-h Week, Monday Night Start (5 days × 8 h per day) Application Second shift for continuous construction with break for eve- ning rush hour traffic. May be used with 5-h closures (e.g., 10:00 p.m. to 3:00 a.m.) in urban areas that require longer periods for morning and evening rush hours (e.g., New York, Los Angeles). Shift Start Time: 8:00 p.m. Shift End Time: 4:30 a.m. Bedtime, After Shift: 6:30 a.m. Wake Up, After Shift: 1:00 p.m. Total Sleep, After Shift: 6.5 h Assumptions • 30-min meal break • 1-h commute • 1 h of “down time” between arriving home after work and going to bed • 1:00 p.m. wake time Fatigue Profile Fatigue level rises steeply throughout the shift and commute home to a maximum just before going to bed. Peak fatigue increases each shift until early Saturday morning. Very high fatigue levels during shifts are primarily the result of being awake during a phase in the circadian cycle when there is sub- stantial pressure to sleep. The progressive increase in overall fatigue throughout the week (cumulative fatigue) is the result of sleep loss while working night shift. Sleep durations are significantly shorter than for day shifts because of circadian

112 rhythm influences: for shifts ending at 4:30 a.m., a maximum sleep duration of 6.5 h due to circadian pressure to wake around 1:00 p.m. (Figure D.6.). Preventive Countermeasures • Defensive nap in the afternoon before beginning night shift. • Return to day schedule (sleeping at least 8 h per night) on days off, following a morning nap on 1st day off from nights. • Sleep in on the weekend to make up for sleep loss during the week. Operational Countermeasures • Caffeine during the shift, but no later than 5 h before bedtime. • Strategic naps (on the job) to reduce impact of shortened sleep periods. A mid-shift nap substantially reduces peak fatigue within and across shifts and reduces cumulative fatigue. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. • Supervisory monitoring for signs of fatigue and applica- tion of countermeasures. Comments • With each of the following conditions there is the poten- tial for fatigue to accumulate over time as sleep duration declines: 44 Shifts that end later than 4:00 a.m. (see variations) will lead to reduced sleep durations due to circadian pressure to wake around 1:00 p.m. Longer night shifts tend to end later, resulting in later bedtimes; long night shifts should be used sparingly. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to a later bed time. • Returning to a day schedule on days off may not substantially increase sleep duration compared with staying on a night schedule, but it is likely to result in improved sleep quality and less disruption to daily activities. Night Shift Schedule Variations The same assumptions, recommended countermeasures, and general comments apply for all night shift variations. 48-h Week, Monday Night Start (4 nights × 10 h per night, 1 night × 8 h) Application Second shift for continuous construction with break for evening rush hour traffic. Potential for use with 8-h closures (e.g., 9:00 p.m. to 5:00 a.m.) in urban areas. Shift Start Day: Mon. to Thur. Friday Shift Start Time: 7:30 p.m. 7:30 p.m. Shift End Time: 6:00 a.m. 4:00 a.m. Bedtime, After Shift: 8:00 a.m. 6:00 a.m. Wake Up, After Shift: 1:00 p.m. 1:00 p.m. Total Sleep, After Shift: 5 h 7 h Figure D.6. Fatigue profile: night shift schedule ending at 4:30 a.m.

113 50-h Week, Monday Night Start (5 nights × 10 h per night) Application Second shift for continuous construction with break for eve- ning rush hour traffic. May be used with 7-h closures (e.g., 10:00 p.m. to 5:00 a.m.) in urban areas. Shift Start Time: 8:00 p.m. Shift End Time: 6:30 a.m. Bedtime, After Shift: 8:30 a.m. Wake Up, After Shift: 1:00 p.m. Total Sleep, After Shift: 4.5 h 55-h Week, Monday Night Start (5 nights × 11 h per night) Application Second shift for continuous construction with break for eve- ning rush hour traffic. May be used with 8-h closures (e.g., 9:00 p.m. to 5:00 a.m.) in urban areas. Shift Start Time: 7:00 p.m. Shift End Time: 6:30 a.m. Bedtime, After Shift: 8:30 a.m. Wake Up, After Shift: 1:00 p.m. Total Sleep, After Shift: 4.5 h 60-h Week, Monday Night Start (5 nights × 12 h per night) Application Second shift for continuous construction with break for evening rush hour traffic. May be used with 11-h closures (8:00 p.m. to 7:00 a.m.) in rural areas where there is little or no rush hour traffic. Shift Start Time: 7:00 p.m. Shift End Time: 7:30 a.m. Bedtime, After Shift: 9:30 a.m. Wake Up, After Shift: 1:00 p.m. Total Sleep, After Shift: 3.5 h Comment on Night Shift Variations • Peak fatigue levels and cumulative fatigue effects become more pronounced as shift end times get later, but the same general pattern holds for all night-shift variations. 55-H Weekend Closure, day Shift Day Shift, 50-h Week Base Schedule (5 days × 10 h per day on weekdays, 2 days × 12 h per day on weekend, for 12 consecutive days worked) Application Accelerated schedules, daytime portion of two-shift continu- ous construction with break for evening rush hour traffic during the week, switching to 12-h shifts for closure period. Used with 55-h (10:00 p.m. Friday to 5:00 a.m. Monday) weekend closure. Mon.–Fri. Sat.–Sun. Mon.–Fri. Week 1 (closure) Week 2 Shift Start Time: 7:00 a.m. 7:00 a.m. 7:00 a.m. Shift End Time: 5:30 p.m. 7:30 p.m. 5:30 p.m. Bedtime: 10:00 p.m. 10:00 p.m. 10:00 p.m. Wake Up: 5:30 a.m. 5:30 a.m. 5:30 a.m. Assumptions • 30-min meal break • 1-h commute • 7.5 h of sleep nightly • 30 min of personal time between waking up and starting work Fatigue Profile Fatigue peaks just after noon, declines toward evening, and then rises sharply before bedtime (Figure D.7.). Preventive Countermeasures • Consider selective half or full shift off following closure to provide recovery opportunity. • Maintain consistent sleep and wake times throughout the week. • Maintain similar or identical sleep and wake times on week- end or nonwork days. Operational Countermeasures • Caffeine during day, but no later than 4:00 p.m. • Strategic naps (on the job) to reduce impact of restricted sleep. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks.

114 Comments • While this example uses a 50-h week as the “base” schedule, the fatigue profile, assumptions, and countermeasures also apply to longer and shorter shift durations within this schedule type. • With each of the following conditions there is the potential for fatigue to accumulate over time as sleep duration declines: 44 Shifts that are longer than 10 h (e.g., during closure) may lead to reduced sleep durations due to a later arrival time home and the need for additional time for per- sonal activities. 44 Shifts that begin before 7:00 a.m. may lead to reduced sleep durations because individuals may not be able to compensate for an earlier wake time by going to bed earlier. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to both an earlier wake time and a later arrival time home. 55-Hour Weekend Closure, Night Shift Night Shift, 50-h week Base Schedule, Monday Night Start (4 nights × 10 h per night 1st week, 3 nights × 12 h per night on weekend, 5 nights × 10 h per night second week, for 12 consecutive nights worked) Application Accelerated schedules, nighttime portion of two-shift con- tinuous construction (7-h urban night closure during week) with break for evening rush-hour traffic during the week, switching to 12-h shifts for closure period. Used with 55-h (10:00 p.m. Friday to 5:00 a.m. Monday) weekend closure. Shift Start Day: Mon.–Thur. Fri.–Sun. Mon.–Fri. Week 1 (closure) Week 2 Shift Start Time: 8:00 p.m. 7:00 p.m. 8:00 p.m. Shift End Time: 6:30 a.m. 7:30 a.m. 6:30 a.m. Bedtime, After Shift: 8:30 a.m. 9:30 a.m. 8:30 a.m. Wake Up, After Shift: 1:00 p.m. 1:00 p.m. 1:00 p.m. Total Sleep, After Shift: 4.5 h 3.5 h 4.5 h Assumptions • 30-min meal break • 1-h commute • 1 h of “down time” between arriving home after work and going to bed • 1:00 p.m. wake time Fatigue Profile Fatigue level rises steeply throughout the shift and commute home to a maximum just before going to bed. Peak fatigue Figure D.7. Fatigue profile: 55-h closure, day-shift schedule.

115 increases each shift until early Saturday morning. Very high fatigue levels during shifts are primarily the result of being awake during a phase in the circadian cycle when there is sub- stantial pressure to sleep. The progressive increase in overall fatigue throughout the week (cumulative fatigue) is the result of sleep loss while working night shift. Sleep durations are significantly shorter than for day shifts because of circadian rhythm influences: for shifts ending at 7:30 a.m., a maximum sleep duration of 3.5 h due to circadian pressure to wake around 1:00 p.m. (Figure D.8.). Preventive Countermeasures • Minimize use of extended shifts (10 to 12 h) due to reduced individual crew recovery opportunities. • Consider selective half or full shift off following closure to provide recovery opportunity • Defensive nap in the afternoon before beginning night shift. • Return to day schedule (sleeping at least 8 h per night) on days off, following a morning nap on 1st day off from nights. • Sleep in on the weekend to make up for sleep loss during the week. Operational Countermeasures • Caffeine during the shift, but no later than 5 h before bedtime. • Strategic naps (on the job) to reduce impact of shortened sleep periods. A mid-shift nap substantially reduces peak fatigue within and across shifts and reduces cumulative fatigue. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. • Supervisory monitoring for signs of fatigue and applica- tion of countermeasures. Comments • While this example uses a 50-h week as the “base” schedule, the assumptions and countermeasures also apply to longer and shorter shift durations within this schedule type. Peak fatigue levels and cumulative fatigue effects will vary with shift end time, but the same general pattern holds for all night shift variations. • With each of the following conditions there is the potential for fatigue to accumulate over time as sleep duration declines: 44 Shifts that end later than 4:00 a.m. will lead to reduced sleep durations due to circadian pressure to wake around 1:00 p.m. Longer night shifts tend to end later, resulting in later bedtimes; long night shifts should be used sparingly. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to a later bed time. • Returning to a day schedule on days off may not substan- tially increase sleep duration compared with staying on a night schedule, but it is likely to result in improved sleep quality and less disruption to daily activities. Figure D.8. Fatigue profile: 55-h closure, night-shift schedule.

116 Switching (Rotating) Shifts Switching Day Shift to Night Shift Over Weekend, 50-h Week (5 shifts × 10 h per shift, 2 weeks) Application Used for crew skill mix and schedule management as required (in this example, with 7-h urban closures at night). Day Shift, Week 1 Night Shift, Week 2 Shift Start Time: 7:00 a.m. Shift Start Time: 8:00 p.m. Shift End Time: 5:30 p.m. Shift End Time: 6:30 a.m. Bedtime: 10:00 p.m. Bedtime, 8:30 a.m. After Shift: Wake Up: 5:30 a.m. Wake Up, 1:00 p.m. After Shift: Total Sleep, 4.5 h After Shift: Assumptions • All shifts: 44 30-min meal break 44 1-h commute • While on day shift: 44 7.5 h of sleep nightly 44 30 min of personal time between waking up and start- ing work • While on night shift: 44 1 hour of “down time” between arriving home after work and going to bed 44 1:00 p.m. wake time Fatigue Profile While on day shift (Week 1), fatigue peaks just after noon, declines toward evening, and then rises sharply before bed- time; 7.5 h sleep each night allows full recovery each day. While on night shift (Week 2), fatigue level rises steeply throughout the shift and commute home to a maximum just before going to bed. Peak fatigue increases each shift until early Saturday morning. Very high fatigue levels dur- ing night shifts are primarily the result of being awake dur- ing a phase in the circadian cycle when there is substantial pressure to sleep. The progressive increase in overall fatigue throughout Week 2 (cumulative fatigue) is the result of sleep loss while working night shift. Sleep durations are sig- nificantly shorter than for day shifts because of circadian rhythm influences: for shifts ending at 6:30 a.m., a maxi- mum sleep duration of 4.5 h due to circadian pressure to wake around 1:00 p.m. (Figure D.9.). Preventive Countermeasures • Minimize use of extended shifts (10 to 12 h) at night due to reduced individual crew recovery opportunities. Con- sider reduced shift duration, for example, 8 h for night shift after switching. Figure D.9. Fatigue profile: switching from day shift to night shift over a weekend.

117 • When switching shifts midweek, avoid using double shifts, that is, provide at least a 24-h break between shifts. • Take defensive nap in the afternoon before beginning night shift. • Return to day schedule (sleeping at least 8 h per night) on days off, following a morning nap on 1st day off from nights. • Sleep in on the weekend to make up for sleep loss during the week. Operational Countermeasures: • Caffeine during shift, but no later than 4:00 p.m. (days) or 5 h before bedtime (nights). • Strategic naps (on the job) to reduce impact of shortened sleep periods (nights) or restricted sleep (days). • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. • Supervisory monitoring for signs of fatigue and applica- tion of countermeasures. Comments • While this example uses a 50-h week as the “base” schedule, the assumptions and countermeasures also apply to longer and shorter shift durations for both day and nights shifts, respectively. Peak fatigue levels and cumulative fatigue effects on night shift will vary with shift end time, but the same general pattern holds for all night-shift variations. • Switching from nights to days over a weekend involves reversing the schedule and wake and sleep times shown in this scenario. This direction of switching is much easier for workers, although there will be some residual cumulative fatigue that is resolved throughout the week as they obtain more restorative sleep during 7.5 h episodes. • With each of the following conditions there is the poten- tial for fatigue to accumulate over time as sleep duration declines: 44 Day shifts that are longer than 10 h may lead to reduced sleep durations due to a later arrival time home and the need for additional time for personal activities. 44 Day shifts that begin before 7:00 a.m. may lead to reduced sleep durations because individuals may not be able to compensate for an earlier wake time by going to bed earlier. 44 Night shifts that end later than 4:00 a.m. (see variations) will lead to reduced sleep durations due to circadian pres- sure to wake around 1:00 p.m. Longer night shifts tend to end later, resulting in later bedtimes; long nights shifts should be used sparingly. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to both an earlier wake time and a later arrival time home. • Returning to a day schedule on days off may not substantially increase sleep duration compared with staying on a night schedule, but it is likely to result in improved sleep quality and less disruption to daily activities. Manager, Weekend Closure Manager Anchor Sleep (“Split”) Schedule over 55-h Weekend Closure With significant night-shift and day-shift presence (2 weeks) Application Accelerated schedules requiring manager presence during 55-h (10:00 p.m. Friday to 5:00 a.m. Monday) weekend closure. Base 50-h week schedule before and after weekend closure Shift Start Time: 7:00 a.m. Shift End Time: 5:30 p.m. Bedtime, Work Nights: 10:00 p.m. Wake Up, Workdays: 5:30 a.m. Weekend closure schedule Friday Saturday Sunday Monday Total Work 10 hours 12 hours 12 hours 11 hours Total Sleep 7 hours 7 hours 7 hours 6 hours 5:00 PM 4:00 PM 3:00 PM 2:00 PM 1:00 PM 10:00 PM 9:00 PM 8:00 PM 7:00 PM 6:00 PM 10:00 AM Work Work Anchor Sleep Work 12:00 AM 1:00 AM 12:00 PM 11:00 AM 6:00 AM 5:00 AM 12:00 AM Work Anchor Sleep Work Nap 3:00 AM 2:00 AM 11:00 PM Full Night Sleep 9:00 AM 8:00 AM 7:00 AM Work↓ Work↓ 4:00 AM Nap Work↓ Nap Work Full Night Sleep↓ Work Nap

118 Assumptions • 1-h commute • 7.5 h of sleep nightly during regular work week Fatigue Profile Managers may feel they need to maintain a presence on the job site for as much as possible of the closure weekend. The pri- mary obstacle to getting sufficient rest may be going to bed in a timely manner once off work. While working during the day (“regular” schedule), fatigue peaks just after noon, declines toward evening, and then rises sharply before bedtime; 7.5 h sleep each night allows full recovery each day. While working during the night (closure period), fatigue level rises steeply throughout the work period to a maximum just before going to bed. Peak fatigue increases for each period of work at night. Very high fatigue levels during night work are primarily the result of being awake during a phase in the circadian cycle when there is substantial pressure to sleep. The progressive increase in overall fatigue throughout the closure period (cumulative fatigue) is the result of sleep loss while working at night. However, anchor sleep periods maintain relatively low baseline fatigue levels overall, allow for 11 to 12 h of work daily during closure period, and allow for good fatigue recovery in the subsequent week (Figure D.10.). Preventive Countermeasures • Use anchor sleep to obtain 6 to 8 h in two separate sleep periods as the primary countermeasure. • Consider selective half or full day off following the weekend closure to provide recovery opportunity. Operational Countermeasures • Caffeine during day, but no later than 5 h before bedtime. • Strategic naps (on the job) to reduce impact of shortened sleep periods. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. • Supervisory monitoring for signs of fatigue and applica- tion of countermeasures. Comment • For additional fatigue profiles, countermeasures, and consid- erations that are relevant to managers under other condi- tions, refer to the pages for Day Shift Schedules and variations (for “typical” manager schedules) or to the Designer/Engineer High Production Schedule (for very long work weeks that include weekend hours). Designer/Engineer High Production Schedule Designer/Engineer, 80-h week (5 days × 14 h per day, 1 day × 10 h per day) Figure D.10. Fatigue profile: manager anchor sleep schedule for a 2-week period that includes a 55-h weekend closure.

119 Application Approaching deadline on design work prior to construction. Mon. to Fri. Sat. Shift Start Time: 7:00 a.m. 8:00 a.m. Shift End Time: 9:30 p.m. 6:00 p.m. Wake Up: 5:30 a.m. 6:00 a.m. Bedtime: 11:30 p.m. 10:30 p.m. Total Sleep Nightly: 6 h 7.5 h Assumptions • 30-min meal break • 1-h commute • 30 min of personal time between waking up and starting work Fatigue Profile Fatigue rises noticeably in the early afternoon, declines toward evening, and then rises sharply and peaks just before bedtime. This pattern is similar to a standard day shift, but the progres- sive increase in overall fatigue throughout the week (cumulative fatigue) is the result of sleep loss: The 14-h days in this schedule limit sleep to 6 h per night on weeknights (Figure D.11.). Preventive Countermeasures • Maintain consistent sleep and wake times throughout the week. • Sleep in on the weekend or take naps when able to make up for sleep loss during the week. • Reduce high production designer workload through increased staffing and project planning. Operational Countermeasures • Caffeine during day, but no later than 4:00 p.m. • Strategic naps (on the job) to reduce impact of restricted sleep. • Consume caffeine just before strategic naps to counteract sleep inertia on waking. • Self-selected rest breaks to reduce fatiguing impacts of monotonous tasks or highly complex tasks. Comments • Each of the following conditions can contribute to even greater fatigue accumulation over time as sleep duration declines: 44 Late arrival time home and need for additional time for personal activities can further restrict sleep. 44 Commute times longer than 1 h each way may lead to reduced sleep durations due to both an earlier wake time and a later arrival time home. • For additional fatigue profiles, countermeasures, and considerations that are relevant to designers and engineers under other conditions, refer to the pages for Day Shift Schedules and variations (for “typical” designer/engineer schedules). Figure D.11. Fatigue profile: high production (80 h per week) designer schedule.