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55 ARTICLE SUMMARIES Reviewers: Dianne Davis, Alison Smiley Title: Arnold, P.K., Hartley, L.R., Hochstadt, D., and Penna, F. "Hours of work, and perceptions of fatigue among truck drivers." (1997). Accident Analysis & Prevention, 29 (4) 47177. Abstract: This paper summarizes the results of a survey conducted with 1,249 truck drivers and 84 management representatives of transport companies. Data were collected in an Australian state which, at the time of the survey, did not restrict driving hours for heavy haulage driv- ers. Regulations were being discussed to limit driving to 14 hr in any 24-hr period and restricting driving hours over the week to 72 hr. The aim of the study was to obtain infor- mation about hours of work and sleep from drivers operating in a state without restrictions on driving hours (i.e., unregulated drivers). Drivers were asked to provide details about their driving and non-driving work schedules and the amount of sleep they had obtained in the past week. They were also asked to give an hour-by-hour record of activities, feelings of fatigue, and encounters with dangerous events over the 24 hr prior to the interview. Drivers and company representatives were interviewed about their perceptions about fatigue (e.g., factors perceived to be related to fatigue, causes, management) and whether they felt fatigue was problematic for truck drivers. A definition of fatigue was not provided. The authors concluded the paper by comparing their data on unregulated drivers' perceptions about fatigue to those reported by Williamson et al. (1992) for mainly regulated drivers. Methodology: Survey conducted with 1,249 truck drivers and 84 management representatives of transport companies. Scope of Work: Survey conducted at road houses in Australia with truck drivers. A second questionnaire was used with management representatives of transport companies in the same state. No lit- erature review was reported. Sample Size: 1,249 truck drivers; 84 management representatives Industry Sector: Heavy road transport industry Major Limitations: Study relies on driver's memories of their sleep and work activities as well as fatigue lev- els rather than objective measures. As a definition for fatigue was not provided for drivers or company representatives it is difficult to know how participants were interpreting this concept. In addition, comparisons with other studies must be viewed cautiously, since ques- tions and response options were not identical. Findings 1. In a 24-hr period, approximately 38% of drivers exceeded 14 hr of driving and 51% exceeded 14 hr of driving plus other non-driving work 2. Approximately 17% of unregulated drivers exceeded 72 hr of driving in the week. When non-driving work was added, 30% worked in excess of 72 hr. 3. Approximately 12% of drivers reported less than 4 hr of sleep on 1 or more working days in the week preceding the interview. These drivers were likely to be operating their vehi- cles while having a significant sleep debt. 4. Approximately 20% of drivers who reported having less than 6 hr of sleep before start- ing their current journey reported 40% of the hazardous events. 5. Many drivers and company representatives reported fatigue to be a problem for other drivers but considered themselves or their companies' drivers to be relatively unaffected by fatigue. 6. Nearly 70% of company representatives thought that long hours of driving were a main contributor of fatigue, while only 40% of drivers named long hours. About half the com- pany representatives thought lack of sleep contributed to fatigue while about one-third

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56 of drivers thought so. Companies also identified inexperience as a cause of fatigue more often than did drivers. In contrast, more drivers blamed both loading the truck and delays in loading for their fatigue while fewer company representatives identified these two causes. 7. The authors concluded the paper by comparing their data on unregulated drivers' per- ceptions about fatigue with those reported by Williamson et al. (1992) for mainly regu- lated drivers. The results suggest that unregulated drivers perceive fatigue to be a prob- lem for themselves less frequently than regulated drivers (10% versus 28 to 35%). Similarly, fewer unregulated drivers considered fatigue to be a general industry problem than did regulated drivers (39% versus 78%). These differences in frequency ratings may be due to differences in the attention paid to fatigue as a safety problem in regulated and unregulated states. In addition, it is possible that regulated drivers experience more fatigue because of long driving hours and less discretion to rest, than do the unregulated drivers. However, the authors caution that, in comparing the two studies, one must bear in mind that each asked different questions of drivers' perceptions of fatigue and pro- vided different response options. Findings Directly Related Driver Fatigue/Alertness to HOS (include page references): p. 476, "Twelve percent of drivers who reported having had a crash in the previous 9 months identified fatigue as a contributing factor." p. 476, ". . . drivers appear to be over confident about their own resilience to fatigue even though they recognize that others are at risk of experiencing fatigue while driving." p. 473, "Five percent of the unregulated drivers reported having experienced a hazardous, fatigue related event, such as nodding off, on their current journey." p. 473, ". . . 20% of drivers who reported having had less than 6 hours sleep reported 40% of the hazardous events." Driver Duration p. 472, ". . . 38% of drivers exceeded or would exceed 14 hours of driving in the 24 hour period. When other non-driving work was taken into account, the proportion exceeding 14 hours of work per 24 hour period increased by about 13%." p. 472, ". . . 17.5% of unregulated drivers exceeded 72 hours of driving in the week. When non-driving work is added, 30% worked in excess of 72 hours." Driver Health No significant findings or assumptions concerning impact on health. Reviewer's Notes: This paper was one of several in a special issue of the journal Accident Analysis & Pre- vention that focused on fatigue and transport.

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57 Reviewers: Dianne Davis, Alison Smiley Title: Baas, P.H., Charlton, S., and Bastin, G. "Survey of New Zealand truck driver fatigue and fitness for duty." (2000). 4th International Conference on Fatigue and Transportation, Fre- mantle, Western Australia. Abstract: This paper summarizes the results of a survey of truck driver fatigue in New Zealand. Inter- views and performance tests were collected from truck drivers at various locations through- out the North Island of New Zealand throughout the day and night. In an analysis of the first 100 drivers, the researchers found that a sizable number of drivers exceeded the allowable driving hours. They also found high levels of fatigue and sleepiness and differences between line-haul and local delivery drivers. Methodology: A survey was conducted with 600 truck drivers at depots, markets, and so forth around the North Island of New Zealand. Interviews focused on "driver demographic and work/rest patterns, drivers' attitudes toward fatigue, propensity toward daytime sleepiness, and a self- assessment of drivers' momentary level of fatigue. A simulator-based performance test of driving was also undertaken on an adapted version of the commercially available truck operator proficiency system (TOPS). "In the course of its development, TOPS passed through several verification and validation stages resulting in a pass/fail criterion for driver performance." The performance test consisted of a standard driving task, a dual-axis sub- critical tracking task, and a tertiary or side-task requiring driver monitoring and periodic responses. "Calculation of pass/fail scores was based on five performance index coefficients (linear combinations of the performance variables). For each driver the five performance indices were calculated and compared to established performance criteria for each of the indices. The five indices, although composed of different weightings of the variables, can be characterized as focusing on the following five general categories: curvative error vari- ability, divided attention response time variability, throttle activity variability, steering activity variability, and longitudinal speed variability. A driver was required to obtain a passing score on each of the five performance indices in order to receive a passing score for the trial as a whole." Scope of Work: Interviews and simulator-based performance tests conducted at depots, wharves, markets, and other locations throughout the North Island of New Zealand throughout the day and night. Sample Size: 600 truck drivers ranging from 19 to 59 years of age (average age = 36; average years of experience = 13.76 years) Industry Sector: Truck drivers (74% company employee drivers, 20% subcontractors, 4% working for owner/drivers, 2% independent owner/drivers) Major Limitations: Study summarizes only initial results of the first 100 drivers. Selected performance indices are not necessarily valid predictors of crash risk. Findings 1. "The drivers' typical workday length ranged from 6 to 15 hr with an average across all drivers of 11.89 h and a S.D. of 1.683." 2. "The average number of days driving per week ranged from 3 (relief and part-time driv- ers) to 7, with an average of 5.35 days, standard deviation of 0.557 days." 3. Drivers typically rated fatigue to be a problem for other drivers more often than for themselves. 4. A much lower percentage of drivers rated fatigue as "never" being a problem for them than did drivers in Hartley et al.'s study (13% as opposed to 35.5% in Hartley et al.). 5. Large numbers of drivers did not comply with the HOS regulations.

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58 6. Drivers had an average of just 1.5 meals per day (0.5 of a meal was defined as a light snack, usually while driving). 7. The average Epworth Sleepiness Score of 7.53 (S.D. of 4.47) was substantially higher than the average score of 5.7 for truck drivers and 6.2 for automobile drivers reported in previous research (Maycock 1995). 8. Of all drivers, 91% passed all five performance criteria for the performance test on the simulator. "Of the 9% of drivers displaying driving performance below the criterion level, eight drivers failed the first performance criterion, a linear combination of mea- sures predominantly associated with curvature error variability." 9. "Of the drivers' activity and demographic measures, two were found to be particularly reliable predictors of simulator task performance: average distance driven per shift and driver age, F (2, 98) = 8.42, P < 0.01. Drivers with an average daily route of fewer than 250 km and drivers 37 years and older were much more likely to fail the performance test." The authors noted that at this stage it was unclear "how to interpret the route length and age effects in the TOPS results." Findings Directly Related Driver Fatigue/Alertness to HOS (include page references): p. 188, Baas, "The drivers typically rated fatigue to be a problem for other drivers (21% rating it always or often a problem) more often than for themselves (8% rating it a prob- lem always or often)." p. 476, "The average Epworth Sleepiness Score of 7.53 (S.D. of 4.47) in our sample is sub- stantially higher than the average score of 5.7 for truck drivers and 6.2 for automobile driv- ers reported in previous research (Maycock 1995)." Driver Duration p. 188, Baas, "The drivers' typical workday length ranged from 6 to 15 hr with an average across all drivers of 11.89 h and a S.D. of 1.683." p. 188, Baas, "The average number of days driving per week ranged from 3 (relief and part- time drivers) to 7, with an average of 5.35 days, standard deviation of 0.557 days." p. 188, Baas, "The results of the activity survey provide clear evidence that large numbers of drivers are not complying with the hours of service regulations" (i.e., no more than 11 hours on duty? Driving?, with at least 9 consecutive hours of rest between driving shifts. " Thirty-three percent of drivers admitted to driving longer than 11 h in 24, and only 69% of drivers reported at least 9 consecutive hours of rest (9 hours sleeping plus hours relax- ing) between driving shifts." Driver Health No significant findings or assumptions concerning impact on health.

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59 Reviewers: Dianne Davis, Alison Smiley Titles: Balkin, T., Thome, D., Sing, H., Thomas, M., Redmond, D., Wesensten, N., Williams, J., Hall, S., and Belenky, G. (2000). "Effects of sleep schedules on commercial motor vehicle driver performance." Department of Transportation, Federal Motor Carrier Safety Administration. FMCSA Tech Brief, 2000/09 (FMCSA-MCRT-00-015). "Effects of sleep schedules on commercial motor vehicle driver performance--Part 2." N.B. In the summary of this study, not all direct quotes are indicated as such. Abstract: A study was conducted to gather and analyze data on CMV driver rest and recovery cycles, effects of partial sleep deprivation, and prediction of subsequent performance. The project was composed of two studies. The first study was a field study using wrist actigraphy to determine sleep duration and timing in long- versus short-haul CMV drivers over 20 con- secutive days. The second study was a sleep dose/response (SDR) laboratory study on CMV drivers to determine the effects of 3, 5, 7 and 9 hr time in bed on performance (including simulated driving) over 7 consecutive days. The findings from the laboratory study were used to "optimize the parameters of the Walter Reed Sleep Performance model (SPM)--a mathematical algorithm to predict performance based on prior sleep and circadian rhythm. Methodology: Field Study Study involved actigraphic assessment of sleep and driver/sleep logs, conducted with long- and short-haul CMV drivers over 20 consecutive days. The drivers wore the Walter Reed wrist actigraphs at all times except when bathing or showering. In addition they completed sleep logs on driver's daily log sheets to gather subjective information about sleep times, sleep latency, arousals during sleep, alertness upon awakening, naps (number and duration), and self-reported caffeine, alcohol, and drug use. The data from each actigraph were downloaded to a personal computer, and each 24-hr actigraph recording period was examined for sleep in its entirety regardless of the duty status type or length indicated on the daily log sheet. Laboratory Study Primary objectives of the laboratory study were to "(1) determine the effects of four sleep/wake schedules on alertness and performance and (2) develop an algorithmic model to predict performance on the basis of prior sleep parameters." Drivers had 3 days of ori- entation and baseline sleep in the laboratory before data collection commenced over 7 days of performance testing with 3, 5, 7, or 9 hr of sleep each night. The recovery period, that followed, lasted 4 days with 8 hr in bed each night. A wide variety of measures were used. Measures consisted of the psychomotor vigilance task (PVT), the cognitive performance assessment battery, driving simulator tasks (e.g., lane tracking) as well as sleep latency, EMG, and sleepiness ratings. In addition to these measures, a number of health measures were taken (e.g., tympanic temperature, heart rate, and blood pressure). Primary objectives of the laboratory study were to (1) determine the effects of four sleep/wake schedules on alertness and performance and (2) develop an algorithmic model to predict performance on the basis of prior sleep parameters." Scope of Work: Historical and methodological overview of sleep and performance, description of sleep/ performance model, field study using actigraphs, laboratory study of effect of sleep restric- tion on performance. Sample Size: Field Study: 50 long- and short-haul CMV drivers ages 21 to 65; Lab Study: 66 CMV driv- ers (16 females, media age = 43; 50 males, mean age = 37)

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60 Industry Sector: Long- and short-haul driving Major Limitations: Field Study Actigraphy does not allow scoring of sleep stages, which may be differentially restorative. The reliability of actigraphy in a moving motor vehicle (e.g., when a driver is sleep- ing in a sleeper berth of a moving vehicle) is currently unknown. The reliability of subjective reports (e.g., subject logs) is typically low. Two potential sources of error were uncovered during this study: Time zones: Some drivers' company work sites were in a time zone different from the time zone in which the driver resided. Shifts to and from Daylight Saving Time (DST): Several drivers participated dur- ing shifts to or from DST. These shifts were reflected in the RODS (Driver's Daily Log Sheets), but not in the actigraph data. These times had to be identified and the actigraph data adjusted to match the RODS. The strength of this study is that all periods of sleep, not just those taken off-duty, were recorded for a large group of CMV drivers over an extended period of time. Laboratory Study Study only looked at daytime driving. Recovery sleep was restricted to 8 hr. The trade-off for using a wide variety of measures was that the number of daily admin- istrations for each particular measure was restricted--precluding evaluation of circa- dian rhythms in this study. Subjects were heterogeneous with respect to age, which may have contributed to error variance in performance measures. Findings Field Study 1. Both long- and short-haul drivers averaged approximately 7.5 hr of sleep per night, which is within normal limits for adults. "However, the short-haul drivers tended to con- solidate their daily sleep into a single, off-duty period, whereas long-haul drivers obtained approximately half of their daily sleep total as daytime naps and/or during sleeper-berth time." 2. As long-haul drivers obtained almost half of their daily sleep during work-shift hours (mainly sleep-berth time), it appears that they spend a significant portion of the work shift in a state of partial sleep deprivation, until the opportunity to obtain on-duty recov- ery sleep presents itself. 3. There was no off-duty duration that guaranteed adequate sleep for the long- or short- haul drivers. As drivers likely use a substantial portion of their off-duty time to attend to personal business, off-duty time must be of sufficient duration to allow drivers to accomplish these tasks and to obtain sufficient sleep. This may be particularly impor- tant for long-haul drivers, who often did not sleep at all during off-duty periods. 4. The bulk of the first (main) daily sleep bouts for short-haul drivers were initiated between 2000 and 0200. Sleep bouts initiated at these times lasted longer (i.e., clustered between 6 and 10 hr) than sleep bouts initiated at other times of day. Several of the sleep bouts initiated between these times lasted longer than 12 hr. 5. Similar to the short-haul drivers, the majority of long-haul drivers' first sleep bouts were initiated between 2200 and 0359. However, long-haul drivers initiated their first sleep bouts more frequently during 0000 and 0359. The duration of long-haul drivers' first sleep bouts clustered between 6 and 10 hr in duration. Sleep bouts exceeding 10 hr in duration

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61 were uncommon and none exceeded 12 hr. Some sleep bouts were initiated in the early and late afternoon hours (1200 to 1959) and, unlike short-haul drivers, almost half of the first sleep bouts initiated during this time frame were longer than 4 hr in duration. 6. There were large day-to-day variations in total sleep time for drivers in both groups. Sleep times varied for some long- and short-haul drivers by up to 11.2 hr across the 20 study days for the long and short-haul drivers. Other drivers maintained more consistent sleep/wake schedules. Some showed a pattern that suggested chronic sleep restriction with intermittent bouts of extended recovery sleep. The authors felt that this suggested that although work-rest schedules could be devised to help minimize CMV driver sleep debt, optimal enhancement of driver alertness and performance would require additional and imaginative approaches. Laboratory Study 1. On average, subjects slept 2.9, 4.7, 6.3, and 7.9 hr for the 3-, 5-, 7-, and 9-hr time in bed conditions respectively, and displayed dose-dependent performance impairment related to partial sleep loss. (As can be deduced from these sleep times, as sleep restric- tion was more pronounced, sleep latency periods declined, resulting in greater sleep efficiency or proportionally more sleep in the available period.) 2. Performance in the 3-hr sleep group typically declined below baseline within 2 to 3 days of sleep restriction. 3. Performance in the 5-hr sleep group was consistently lower than performance in the 7- and 9-hr sleep groups. 4. Performance in the 7- and 9-hr sleep groups was often indistinguishable and improved throughout the study. However, the authors did note that "even a relatively small reduc- tion in average nighttime sleep duration (i.e., 6.3 hr of sleep--the average amount of sleep obtained by the 7-hr group) resulted in measurably poorer performance, for exam- ple, on the PVT. This decrement was maintained across the entire consecutive days of sleep restriction. 5. Virtually no negative effects on performance were seen in the 9-hr sleep group. 6. Sleep restriction effects were consistent. The degree to which "sleep restriction impaired performance was measure-specific." "Across tasks, speed and throughput were con- sistently affected." "In general, performance for the 3- and 5-hour sleep groups was below that of the 7- and 9-hour sleep groups." "Thus, restricting sleep resulted in dose- dependent performance impairment." 7. All cognitive tasks were sensitive to differential sleep restriction. 8. The PVT was the most sensitive measure. (It was also the performance measure which was the most resistant to changes in performance due to learning, an important issue when effects over many days are being examined.) Even the 7-hr group with 6.3 hr of sleep showed decreased performance using this measure across the 7 days. 9. The majority of driving performance measures (e.g., increased lane-tracking variabil- ity increased driving speed, increased speed variability, and increased running-off-road accidents) also showed dose-dependent and/or cumulative sleep restriction effects. 10. Following chronic sleep restriction, the first 8 hr in bed (6.5 hr of sleep) was insuffi- cient for restoration of performance on the PVT task. 11. During the 4-day recovery phase (8 hr in bed each night), 5- and 7-hr sleep groups showed minimal or no recovery, remaining consistently below the 9-hr sleep group and below their own baseline levels for the PVT. 12. The 3-hr sleep group showed some recovery for the PVT on the first day and more on subsequent days but also remained well below their own baseline and below the per- formance of the other groups. 13. Subjects' recovery to baseline or near baseline levels of performance on the PVT often required a second or third night of recovery sleep.

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62 14. These data suggest that after sleep debt has occurred (3, 5, 7 hr time in bed) a single bout of 8 hr of night sleep leads to recovery but not full recovery. While further sleep is required for full recovery, the number of subsequent sleep periods to reach full recov- ery is unknown. For the 3-hr group, the data suggests that even 3 nights of normal sleep (8 hr spent in bed on each night) is not sufficient to restore performance to baseline lev- els (depending on the task). This suggests that full recovery from substantial sleep debt requires recovery sleep of extended duration (i.e., more than 8 hr of normal-duration sleep). This is a unique finding and requires replication. 15. In contrast to the findings concerning PVT performance, the accident rate went back to baseline after 1 recovery day for all groups. In addition, lane position variability was near, but not quite back to baseline for all but the 9-hr group. On recovery days, lane position variability was slightly worse for the 9-hr group who, after being allowed 9 hr in bed each night during the work period, were restricted to 8 hr of sleep. 16. None of the physiological health measures (heart rate, blood pressure) evaluated in this study were sensitive to sleep restriction. 17. "Overall highest HR (collapsed across day and time of day) was seen in the 3-hr group (mean BPM = 79.74) and 7-hr sleep group (mean BPM = 78.64), while lowest HR was seen in the 9-hr sleep group (mean BPM = 70.46) and 5-hour sleep group (mean BPM = 75.48; group main effect, p < 0.05)." 18. "Across study days (collapsed across sleep group and time of day), highest HRs occurred across the last four days . . . while the lowest HR was observed on day E2." 19. "Within days (collapsed across day and sleep group), the highest HR occurred at 1930 hours (mean BPM -79.87), whereas the lowest HR occurred at 1630 hours (mean BPM -72.60; time-of-day main effect, p < 0.05)." 20. Systolic blood pressure did not differ among sleep groups, nor did sleep group interact with day or time of day. 21. The highest systolic blood pressure (SBP) was found on day E4, the fourth experi- mental day, while the lowest SBP occurred on Day R2, the second recovery day. With respect to time of day, the highest SBP occurred at 1320, while the lowest SBP occurred at 0715. 22. "Diastolic pressure did not vary as a function of sleep group or day, nor did these fac- tors interact (main effects and interactions, ns)." 23. "Diastolic pressure varied across the day (time-of-day main effect, p < 0.05)--the high- est DBP values occurred at 0715 hours, and the lowest DBP occurred at 1025 hours. DBP values at 1320, 1625, and 1920 were intermediate between 0715 and 1025 hours and similar among each other." Findings Directly Related Driver Sleep to HOS (include page references): p. ES-5, Field Study: ". . . both long- and short-haul drivers averaged approximately 7.5 hours of sleep per night, which is within normal limits for adults." p. ES-5, Field Study: "Time off-duty was positively correlated with total sleep time for both groups, but the short-haul drivers were more likely to consolidate their daily sleep into a single, work-shift sleep period." p. ES-5, Field Study: "Long-haul drivers obtained almost half of their daily sleep during work-shift hours (mainly sleeper-berth time), which suggests that they spend a significant portion of the work shift in a state of partial sleep deprivation--i.e., until the opportunity to obtain on-duty recovery sleep presents itself." p. ES-5, Field Study: ". . . there was no off-duty duration that guaranteed adequate sleep. . . ." p. ES-5, Field Study: ". . . large day-to-day variations in total sleep time were evident for drivers in both groups. . . ."

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63 Driver Performance p. ES-8, Lab Study, ". . . even a relatively small reduction in average nighttime sleep dura- tion (i.e., 6.28 hours of sleep--the average amount of sleep obtained by the 7-hour group) resulted in measurably decremented performance (e.g., on the PVT). This decrement was maintained across the entire 7 consecutive days of sleep restriction, suggesting that there was no compensatory or adaptive response to even this mild degree of sleep loss." p. ES-8, Lab Study, ". . . the extant level of daytime alertness and performance capacity is a function not only of an individual's circadian rhythm, time since the last sleep period, and duration of the last sleep period, but is also a function of his/her sleep history, extending back for at least several days." Driver Recovery p. ES-8, Lab Study, ". . . following more severe sleep restriction (e.g., the 3-hr group), recovery of performance was not complete after 3 consecutive nights of recovery sleep . . . this suggests that full recovery from substantial sleep debt requires recovery sleep of extended duration. Driver Health p. 2-88, Lab Study, "These results do not support the notion that physiological measures can serve as indices of subtle changes in cognitive performance capacity following sleep loss . . . To date, there is only limited evidence that sleep restriction, or sleep deprivation, affects physiological systems under involuntary control. In fact, none of the physiological health measures evaluated in this study (heart rate, respiration, and blood pressure) were sensitive to sleep restriction. These results also are consistent with the view that sleep depri- vation mainly impairs higher-order cognitive performance."

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64 Reviewers: Dianne Davis, Alison Smiley Titles: Dingus, T., Neale, V., Garness, S., Hanowski, R., Keisler, A., Lee, S., Perez, M., Robin- son, G., Belz, S., Casali, J., Pace-Schott, E., Stickgold, R., and Hobson, J.A., The Impact of Sleeper Berth Usage on Driver Fatigue. FMCSA, FMCSA-RT-02-050, Washington, DC, November 2001. Federal Motor Carrier Safety Administration. "Impact of sleeper berth usage on driver fatigue: Final Report." (2002). Report Number: FMCSA-RT-02-070. Klauer, S.G., Dingus, T.A., Neale, V.L. and Carroll, R.J. (2003) "The effects of fatigue on driver performance for single and team long-haul truck drivers." Driving Assessment 2003--The Second International Driving Symposium on Human Factors in Driver Assess- ment, Training and Vehicle Design. Park City, Utah. N.B. All quotes are from FMCSA summary. Abstract: This report documents research that was conducted on sleeper-berth usage. In addition to focus groups with long-haul operators, a field study was conducted on sleeper-berth usage for single and team drivers. The report outlines a number of factors, discovered in the focus groups, which are important to successful sleeper-berth usage for single and team drivers. Based on the results of the focus group and an accompanying literature review the researchers designed an on-road study with 56 drivers (47 male, 9 female; mean age = 42.6) constituting 13 teams and 30 single drivers to assess the effects of sleeper-berth usage on sleep, driver error, and critical incidents. Methodology: Focus Groups: Ten focus groups were conducted in 8 cities, across 7 states. Field Study: Long-haul truck drivers operated heavy trucks for a minimum of 6 continuous days, with the typical run being 7 to 10 working days, on their regularly assigned route. Data collec- tion systems were installed on the tractors used by the drivers to collect sleeper-berth envi- ronmental data, driving performance information, video of the driver's face, and subjective alertness ratings and data from the Nightcap sleep system. Data (i.e., computer and video) were collected before and during critical incidents such as lane and steering deviations. Scope of Work: Based on the findings of the focus groups and a literature review, a field study protocol was developed to assess the impact of sleeper berth usage. The field study was designed to deter- mine relationships between sleep quality, driver alertness, and driving performance. Sample Size: Focus Groups: 74 participants (27 to 70 years of age). Field Study: 56 drivers participated in the field study (30 single drivers and 13 teams of driv- ers; 7 females, 49 males; mean age = 42.6). Industry Sector: Long-haul operators Major Limitations: n/a Findings Focus Groups 1. "Team versus single driving was identified as a very important factor for drivers relat- ing to quality of sleep." Drivers either loved or hated team driving and discussed vari- ous issues relevant to their preference (e.g., trust, partner's driving ability, driving smoothly, etc.). Drivers also discussed various equipment issues with respect to com- fortable sleeping arrangements (e.g., noise, air-ride vs. spring-ride trucks, etc.).

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65 Field Study: Team Driving vs. Single Driving 2. Single drivers were involved in significantly more critical incidences than team drivers. They were involved in "four times the instances of "very/extremely drowsy" observer ratings than were team drivers, and were more likely to push themselves to drive on occasions when they were very tired." 3. More than one-half of the most severe of the critical incidents were caused by 4 of the 30 single drivers. In contrast, team drivers were generally very successful at avoiding circumstances of extreme drowsiness, drove much less aggressively, and made fewer errors than single drivers. 4. The main effect for segment of day was significant (p < 0.05). Team drivers tended to exhibit critical incidents associated with extreme fatigue during the morning and night hours (morning: 0400 to 1159; afternoon: 1200 to 1759; night: 2200 to 0359). Single drivers "tended to show fewer extreme fatigue-related critical incidents during the morn- ing hours, with gradually more critical incidents being attributed to the very drowsy cat- egories during the evening and nighttime hours." The authors note that single drivers "were exhibiting signs of extreme fatigue during all hours of the day while team drivers only showed signs of fatigue during the nighttime and morning hours." 5. Overall, team drivers were able to better manage their fatigue and critical incident involvement than were single drivers. This may be because team drivers are more likely to effectively trade-off driving duties with their partner before to becoming extremely fatigued. It is also possible that in effect, drivers undergo a natural "screening" process. Focus group participants noted that team drivers must be trustworthy with regard to their driving ability and be considerate of their resting partner. Field Study: Quality of Sleep 6. A number of findings indicated that the quality and depth of sleep was worse (e.g., more sleep disturbances) on the road, particularly for team drivers. They found that while the vehicle was in motion, the noise and motion environment in the sleeper berth degraded the drivers' sleep. Field Study: Hours of Service 7. "In terms of hours of service violations, based on a report by Wylie et al. (1996), there were relatively few instances (about 2.2%) of "extreme drowsiness," with most of these instances being experienced by single drivers, again with a high rate of the occurrence of this level of fatigue on the second or third shift after the first day of a multi-day drive." There were relatively few instances of "extreme drowsiness" (2.2%), with most of these instances being experienced by single drivers, with a high rate of the occurrence of this level of fatigue on the second or third shift after the first day of a multi-day drive." 8. The authors note that it "appears that the combination of long driving times and multi- ple days provides the greatest concern, with several results pointing to the presence of cumulative fatigue." As a result they believe that the length of shifts in the later stages of a trip must also be considered. However, the authors point out that "critical incidents and/or driver errors did not increase directly with the hours beyond the regulation," and that "there was a substantial decrease in the rate of critical incidents during some of the more extreme violations." However, they do caution that this should not be interpreted to mean that HOS should be expanded due to the following two reasons: "First, it may be possible that the drivers were making a point to drive more carefully and cautiously because they were operating outside of the regulation and did not want to get stopped by law enforcement officials. Alternatively, they may have only risked driving outside of the regulations because they felt alert and knew that they could continue to drive safely."

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81 Reviewer: Dianne Davis Title: Morrow, P.C. and Crum, M.R. (2004). "Antecedents of fatigue, close calls, and crashes among commercial motor-vehicle drivers." Journal of Safety Research, 35 (1). Abstract: This paper summarizes the results of a survey of CMV drivers in 116 trucking firms. The pur- pose of the study was to identify factors (i.e., fatigue inducing and company safety manage- ment factors) relevant to the prediction of driving while fatigued, close calls due to fatigue and actual crash involvement among CMV drivers engaged in intra- and interstate truck driv- ing work. "Findings indicated that fatigue-inducing factors inherent in driving work and safety practices accounted for appreciable variation in driving fatigued (R squared = 0.42) and close calls (R squared = 0.35), but not crash involvement. Driving while fatigued also accounted for incremental increases in the amount of variation in close calls, after consider- ation of inherent factors and safety practices." The authors concluded "that safety practices (e.g., establishment of a strong safety culture, dispatcher scheduling practices, company assistance with fatiguing behaviors such as loading and unloading) have considerable poten- tial to offset fatigue-inducing factors associated with truck driving work." Methodology: This paper summarizes the results of a survey of CMV drivers in 116 trucking firms. Thirty- two of these firms were top safety-performing firms, 53 from average firms, and 31 from poor performing firms. Drivers were asked a number of questions about fatigue-inducing factors such workload, schedule regularity, difficulty finding rest places, adequacy of sleep, insufficient recovery, percent of time loading/unloading. In addition, participants were asked about the perceived safety climate in their company. The authors formulated 11 per- ceived safety climate items (e.g., "Our Company makes driving safety a top priority") and asked drivers to record their level of agreement). Finally drivers were asked about their fatigue while driving (e.g., nodding off while driving, etc.,), as well as frequency of close calls and crashes. The authors proposed three models to account for the variation in fatigue while driving, close calls due to fatigue, and crash involvement. Proposition 1 specified that fatigue inducing factors would account for variation in these outcome measures. Proposi- tion 2 specified that "company safety management practices should account for variation in the outcome measures, controlling for fatigue-inducing factors associated with truck driv- ing work." Proposition 3 contended that "fatigue while driving accounts for variation in the frequency of close calls due to fatigue and crash involvement, after controlling for fatigue-inducing factors and company safety management practices." Scope of Work: Survey conducted with CMV drivers. A literature review was conducted on fatigue-inducing factors, work overload, schedule regularity, disturbances in sleep patterns, insufficient recovery, and company safety management practices. Sample Size: Survey of CMV drivers in 116 trucking firms. At least one driver provided usable data from each firm. (4% female, 96% male; ages: 22 to 63; average age = 43; average number of driv- ing years: 14.92). Industry Sector: CMV drivers Major Limitations: The authors conclude their paper with a summary of the limitations of their research. They state that the primary limitations of this research are that it involves "potential sampling bias (e.g., low percentage of firms agreeing to participate in the project, safety director selection of drivers), the use of measures without established validity, and reliance on sin- gle item measures for the independent variables. In addition, they point out concerns with the reliance on driver self-report, and the possible limitation in the restriction in range asso- ciated with the self-report crash involvement measure. Findings 1. "Fatigue-inducing factors inherent in driving work and safety practices" (e.g., schedule regularity, difficulty finding a place to rest, adequacy of sleep when working, insufficient

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82 recovery, percent of time loading/unloading, etc.) "accounted for appreciable variation in driving fatigue (R squared = 0.42) and close calls (R squared = 0.35), but not crash involvement." Self-report measures were used to assess fatigue (i.e., 3-item measure). Crash involvement was measured using the sum of two items: (1) reportable accidents (to the company) and (2) chargeable accidents that drivers had been involved with over the last 2 years. Approximately one-fifth of the drivers reported having one or more reportable accidents, and approximately 4% reported having chargeable accidents. The raw data was adjusted to account for exposure and expressed on a per 100,000 mi basis. Drivers with reportable accidents had between 0.32 and 6.41 crashes per 100,000 mi, while those reporting chargeable accidents had between 0.29 and 1.03 crashes per 100,000 mi. The measure exhibited a Cronbach alpha of 0.85. 2. "Driving while fatigued accounted for incremental increases in the amount of variation in close calls, after consideration of inherent factors and safety practices." 3. ". . . Safety practices (e.g., establishment of a strong safety culture, dispatcher schedul- ing practices, company assistance with fatiguing behaviors such as loading and unload- ing) have considerable potential to offset fatigue-inducing factors associated with truck driving work." 4. While there is an assumption that employees will use off-duty time to engage in restora- tive activities, the insufficient recovery results reported in this study led the authors to con- clude that "drivers do not necessarily spend their non-work time in this manner." While drivers may not engage in job-related activities during their recovery periods, some driv- ers do engage in activities and sleep patterns that lead them to report back to work already fatigued. The authors note that the results "suggest that the potential misuse of off-duty time can be mitigated by the presence of a strong safety climate or enactment of policies targeted at fatigue-inducing activities (i.e., companies can act to reduce this problem)." Findings Directly Related Driver Fatigue/Alertness to HOS (include page references): p. 63, "Insufficient recovery was gauged by asking drivers how frequently they began a new "workweek" feeling tired or fatigued." Just over half (53%) said this never or only rarely happened to them (scored "1") while 47% indicated that this happened with greater fre- quency (scored "2")." p. 65, "Fatigue-inducing factors, especially insufficient recovery, appear to play a role in determining whether a driver experiences fatigue and close calls due to fatigue." p. 65, "The amount of time spent loading and unloading trucks appears to have a bearing on crash involvement, though the overall role of fatigue inducing factors was not predictive of crash involvement."(i.e., more loading and unloading was associated with negative impacts). p. 65, "The joint ability of fatigue-inducing factors and safety practices accounted for 42% (p < .001; Model 1) of the variation in fatigue while driving." p. 66, "Contrary to expectations, policies to minimize driving at night appeared to increase the frequency of close calls due to fatigue. However, it should be noted that policies to min- imize nighttime driving were negatively related (albeit non-significantly) to fatigue while driv- ing (beta = -.10, ns; Model 1), leaving the utility of this practice open to further debate." p. 66, "Schedule regularity, difficulty in finding a place to rest, and insufficient recovery remained statistically significant contributors to the model." p. 66, "Proposition 3 asserted that fatigue while driving accounts for variation in the fre- quency of close calls due to fatigue and crash involvement, after controlling for fatigue- inducing factors and company safety management practices . . . We conclude that Propo- sition 3 was supported in the case of close calls but not in the case of crash involvement."

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83 p. 66, "The models tested herein were able to account for modest amounts, around 40%, of the variation in fatigue and close calls dues to fatigue, but were unsuccessful in explaining crash involvement. While close calls ("near accidents") are often used as proxies for crashes, these findings indicate that each outcome has unique antecedents and thus may require different explanations (e.g., percent of time spent loading was observed to be a good predictor of crashes but not related to fatigue or close calls."). Driver Duration p. 63, "The number of 6-hour time blocks driven in the course of a day was measured by asking drivers to specify the time blocks they normally spent more than 10% of their driv- ing time: 6 a.m. to noon, noon to 6 p.m., 9 p.m. to midnight, and midnight to 6 a.m. . . . Just over half the drivers (50.9%) were able to limit their blocks to two, 27.6% reported three time blocks and 12.5% reported that they commonly worked during all four time blocks." Driver Health No significant findings or assumptions concerning impact on health.

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84 Reviewer: Dianne Davis Title: Williamson, A., Feyer, A., and Friswell, R. (1996). "The impact of work practices on fatigue in long distance truck drivers." Accident Analysis & Prevention, Vol. 28, No. 6, pp. 70971. Abstract: The aim of the study was to investigate the relationship between staged driving and fatigue. Professional truck drivers completed a 12-hr, 900 km trip under each of three driving regimes--a relay (staged) trip, a working hours regulated one-way (single) trip, and a one- way (flexible) trip with no working hours constraints. All of the observed trips took place overnight. The authors concluded "although there was some evidence that fatigue devel- oped differently within the three driving regimes (staged, single, and flexible), the levels of fatigue experienced by drivers increased markedly over all the trips. None of the regimes demonstrated any overall advantage in combating fatigue compared to the other regimes." The authors conclude that it is clear from their findings that even relatively short 12-hr trips are tiring and that effective strategies for fatigue reduction need to be identified. In addi- tion, their finding that pre-trip level of fatigue appears to be an important determinant of later fatigue raises questions about the ongoing work schedules under which long distance drivers operate, "and highlights the need to allow adequate rest and recuperation between trips and between blocks of trips to prevent chronic sleep loss and to reduce fatigue." Methodology: Professional truck drivers completed a 12 hr, 900 km trip under each of three driving regimes--a relay (staged) trip, a working hours regulated one-way (single) trip, and a one- way (flexible) trip with no working hours constraints. "The staged trip entailed driving from Sydney or Melbourne to the trip midpoint (Tarcutta), exchanging trucks or loads with a driver coming in the opposite direction, and then returning to the point of origin." The single one-way trips involved driving directly from Sydney to Melbourne, and the flexible one-way trips involved driving from Melbourne to Sydney." "Under the regulations, drivers on single and staged trips were obliged to break for 30 min after each 5-hr period. Under the flexible regime drivers could choose to take breaks as often or as rarely as they needed with no con- straint on the time taken to complete the trip." All of the observed trips took place overnight. Most trips began in the early evening and night between 1600 and 2359. The three driving regimes did not differ significantly in starting time. While, on average, the staged trips took longer to complete than the flexible trips, the trip lengths differed by only 40 min. The study employed subjective (e.g., Stanford Sleepiness Scale, etc.), physiological (e.g., heart rate), and performance (e.g., speed, steering variability, reaction time, etc.) "measures to examine the relationship between the characteristics of staged driving and the development of fatigue." Scope of Work: Field study with professional truck drivers who routinely ran staged operations between Sydney and Melbourne in Australia. Sample Size: Twenty-seven professional truck drivers (average age = 38.4; average years of commercial driving = 15.9 years Industry Sector: Professional truck drivers Major Limitations: The authors note that further investigation is needed to determine whether these findings would generalize to longer trips where there is greater potential for flexibility in break-taking to be effective. Findings 1. "Although there was some evidence that fatigue developed differently within the three driving regimes (staged, single, and flexible), the levels of fatigue experienced by driv- ers increased markedly over all the trips." 2. "None of the regimes demonstrated any overall advantage in combating fatigue com- pared to the other regimes."

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85 3. It is clear from the findings that "even relatively short 12-hour trips are tiring, and that effective strategies for fatigue reduction need to be identified." 4. Pre-trip level of fatigue appears to be an important determinant of later fatigue. This raises questions about the ongoing work schedules under which long distance drivers operate, "and highlights the need to allow adequate rest and recuperation between trips and between blocks of trips to prevent chronic sleep loss and to reduce fatigue." Findings Directly Related Driver Fatigue/Alertness to HOS (include page references): p. 713, "Both the Stanford Sleepiness Scale ratings and the visual analogue scale ratings (Table 2) revealed a marked increase in fatigue between the beginnings and ends of the trips for all trip types." p.. 713, "Drivers tended to feel most fatigued on staged trips and least fatigued on single trips, however, this pattern was in evidence before driving commenced and at posttrip had not been modified by the intervening driving regime." p. 715, ". . . drivers' performance on the vigilance, critical flicker fusion and unstable tracking tasks suggested heightened fatigue at the start of the staged trip, and for vigilance and unstable tracking, this impaired performance under the staged regime was maintained across the course of the trip. These findings are consistent with the higher fatigue ratings given by drivers before and after the staged trip." p. 717, "Over all measures, the pattern of results suggests that fatigue increased across all trip types . . . There is clearly a need to identify those factors affecting the drivers' pretrip fatigue and performance." p. 718, ". . . the pretrip level of fatigue appeared to be an important determinant of later fatigue. This finding raises questions about the ongoing work schedules under which long distance drivers operate, and highlights the need to allow adequate rest and recuperation between trips and between blocks of trips to prevent chronic sleep loss and to reduce fatigue." Driver Duration p. 712, "The number of breaks taken (Table 1) increased across flexible, single, and staged trips, suggesting an increasing need for rest as a function of driving regime. However, breaks were taken after similar periods of driving for the three trip types (Table 1). The longest driver period (4.5 hours) routinely occurred before the first break and the shortest drive period (2.5 to 3 hours) preceded the second break." p. 712, "In summary, the pattern of break-taking suggests increased fatigue around the middle of the trips and greater overall fatigue on staged trips. However, these conclusions need to be treated cautiously because break-taking may have occurred for reasons other than providing a rest from driving, and at times of convenience, necessity or habit." Driver Health No significant findings or assumptions concerning impact on health.

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86 Reviewers: Dianne Davis, Alison Smiley Title: Williamson, A., Feyer, A.M., Friswell, R., and Finlay-Brown, S. (2000). "Demonstration proj- ect for fatigue management programs in the road transport industry: Summary of findings." Abstract: The aim of this project was to evaluate work-rest schedules to begin to identify some model work-rest schedules to provide companies and drivers flexibility in meeting their opera- tional needs and to manage fatigue most effectively. The paper is a summary of findings of the results of three different reports. Because this paper is a summary of findings, it does not include a great deal of detail. The first report describes the identification of three per- formance measures that have demonstrated sensitivity for detecting fatigue and its effects so that they can be used in developing models of work-rest schedules. The second and third reports focus on on-road and simulated evaluations of current and alternative work-rest schedules. Methodology: The first step in this project involved a comparison of performance on a "range of perfor- mance tests under conditions in which study participants should be tired, with performance under conditions in which they had been exposed to varying doses of alcohol" to identify measures that have demonstrated sensitivity for detecting fatigue. Performance tests were administered at regular intervals over time with increasing sleep deprivation (i.e., partici- pants were kept awake a total of 28 hr) and increasing blood alcohol levels (BAC) (four doses of alcohol to achieve increasing BAC). The authors could then identify which tests were sensitive to increasing alcohol doses and which were sensitive to increasing sleep deprivation. The second and third reports focused on four evaluations, consisting of two evaluations of the current working hours regulations in New Zealand and two evaluations of alternative approaches to work-rest schedules. All the evaluations except one (a simulation) were con- ducted on-road using the performance measures developed in the first step of this project. Participants started the study after being on break for 24 hr to "obtain baseline information about performance when rested." Ratings of fatigue and performance were then taken at "strategic points across the work-rest schedule between two long 24 hour breaks." The alternative approaches to work-rest schedules were evaluated in a simulation study and an on-road study. The simulation study looked at the extension of the daily working hours limit from a "maximum of 14 hours in a 24-hour period to up to 16 hours in a 24-hour period. The overall schedule covered 60 hours. The longer hours were balanced by begin- ning and ending the schedule with a 6-hour break and having a mandatory 6-hour break at some point in the intervening 48 hours. Short breaks of at least 15 minutes were also required after every 3 hours of work. The evaluation was conducted as a simulation because it had not yet been authorized to be trialed on the road as part of the pilot FMP." In con- trast, the second evaluation of an alternative approach to work-rest schedules could be con- ducted on the road because "it was in operation as part of the pilot FMP". It "differed from the regulated hours regime by allowing for longer sustained periods of work at a stretch and splitting of the mandatory breaks between them. The regulated hours allow only 5 contin- uous hours of work before drivers take a break of at least 30 minutes. In this alternative schedule, drivers could work up to 6 continuous hours and only needed to take breaks in 15-minute periods, although they needed to take 30 minutes in total in every 6 hour period. The FMP also allowed drivers to divide the mandatory 6 hour continuous break into shorter sections. In all other ways, the work-rest schedule was the same as the regulated regime." Scope of Work: Identification of performance measures sensitive to fatigue and evaluations of current and alternative working hours regulations. Sample Size: Not stated

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87 Industry Sector: Professional drivers Major Limitations: The evaluation of regulated hours only reflects the effects of one cycle of the current regime on drivers who had low levels of fatigue to begin with. "Further research is needed to look at how the regulated regime manages fatigue over the longer term." Findings 1. While most of the tests showed deterioration in performance with increasing alcohol doses, not all the tests did so for increasing sleep deprivation. 2. The tests chosen to be most sensitive to fatigue were Simple Reaction Time, Mackworth Clock Vigilance test, and Dual Task. 3. ". . . 0.05% BAC equivalence occurred at between 17 and 19 hours of sleep deprivation for most tests. This means that after around 17 hours of wakefulness, performance capac- ity was sufficiently impaired to be of concern for safety." 4. There was little evidence that current working hours led to performance decreases large enough to "constitute a significant safety risk compared to alcohol equivalent levels at 0.05% BAC." 5. In the simulation study of an alternative compliance approach, drivers were able to man- age fatigue effectively over the first 16 hr of the schedule, however, their performance deteriorated significantly by the middle of the second 16-hr period. Performance at this time was "considerably poorer than the 0.05% BAC alcohol equivalence standard. It seems that the 6 hour break was insufficient to allow recovery and recuperation from the demands of the previous long day . . ." The work-rest schedule was "too demanding for drivers to manage fatigue effectively." 6. The results of the road test evaluation of the second alternative compliance approach showed that "reaction speed showed a deterioration across the study to levels that were suggestive of an increased safety risk based on the 0.05% BAC equivalent standard for performance." Findings Directly Related Driver Fatigue/Alertness to HOS (include page references): p. 2, "Through a careful comparison of alcohol and sleep, performance capacity has deteriorated sufficiently to be of concern to the community due to an increased potential safety risk." p. 3, "For the first evaluation of the regulated regime (CR 190, Evaluating a regulated hours regime on-road and an alternative compliance regime under simulated conditions) fatigue ratings were significantly higher when drivers returned to the depot at the end of the first trip and at the end of the study period compared to rested levels. Despite this, there were only a few significant changes in performance capacity." p. 11, For evaluations of regulated regime: "Both evaluations showed, however, that per- formance capacity deteriorates and fatigue levels increase in relation to factors like increasing hours of work (especially night hours), short breaks and breaks that only allow short or poor quantity sleep (see Table 3). While fatigue and performance capacity seem to be maintained with safe limits under the regulated regime, these findings indicate that where drivers or companies take the work-rest schedules beyond the current limits, they are likely to be increasing the risk of performance decrements sufficient to compromise safety." Driver Duration p. 20, "Evaluation of the current working hours regime suggests that provided drivers are rested to begin with, one full cycle of the regulated regime does not produce fatigue or per- formance capacity decrements that are of concern for safety. There is considerable evi- dence however that performance decrements increase significantly as the schedule becomes

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88 more demanding. This is a warning signal for the development of alternative approaches to ensure that schedules are designed that do not simply increase the demands on drivers. The evidence from both evaluations of alternative compliance schedules suggested that they increased the demands on drivers, but did not balance them sufficiently with rest in order to allow recuperation and recovery from accumulated fatigue." p. 20, "These results do not mean that the working hours regulatory regime is the only sat- isfactory approach to managing fatigue. The results show clearly that it is possible to increase trip length to 16 hours, say, and still maintain good performance levels. It is not possible, however, to continue to do 16 hour trips without a longer break than is usually allowed, even in the regulated regime." p. 13, "Long work periods need to be balanced by longer rest periods. This study did not address the issue of the length of rest needed to recover sufficiently from a 16 hour work period. It only showed that a 6 hour break was not sufficient." Driver Health No significant findings or assumptions concerning impact on health are stated in summary.

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89 Reviewers: Dianne Davis, Alison Smiley Titles: Wylie, C.D. "Driver drowsiness, length of prior principal sleep periods, and naps." (1998). Transportation Development Centre. Report No. TP 13237E. Wylie, C.D., Shultz, T., Miller, J.C., and Mitler, M.M. (1997). "Commercial motor vehicle driver rest periods and recovery of performance." Wylie, C.D., Shultz, T., Miller, J.C., Mitler, M.M., and Mackie, R.R. (1996). "Commer- cial motor vehicle driver fatigue and alertness study." (Executive Summary & Technical Summary). Mitler, M.M., Miller, J.C., Lipsitz, J.J., Walsh, J.K., and Wylie, C.D. (1997). "The sleep of long-haul truck drivers." New England Journal of Medicine, 337(11). Freund, D. and Vespa, S. "U.S./Canada study of commercial motor vehicle driver fatigue and alertness." Proceedings of the XIIIth World Meeting of the International Road Federa- tion, Toronto, Ontario. June 1620, 1997. Abstract: This paper summarizes the results of an on-road study with 80 drivers in the U.S. and Canada. The goal of this study was to assess fatigue related to Canadian versus U.S. driv- ing schedules. Data (e.g., loss of alertness, performance, etc.) were collected on drivers for a period of 16 weeks. Drivers drove one of four driving schedules. Time of day was the "strongest and most consistent factor influencing driver fatigue and alertness." In contrast "hours of driving (time-on-task) was not as strong or consistent predictor of observed fatigue." "There was some evidence of cumulative fatigue across days of driving." Methodology: The study used a between-subjects design involving four driving schedule conditions: C1: 10-hr daytime (5 consecutive days); C2: 10-hr rotating (5 consecutive days, starting 3 hr earlier each day); C3: 13-hr nighttime start (4 consecutive days); C4: 13-hr daytime start (4 consecutive days). The study design "was developed to comply with existing U.S. and Canadian hours-of-service regulations." "The four schedules provided different amounts of time off between trips. Condition 1 provided about 11 hours off, while the other three con- ditions provided about 8 hours off." Various measures were taken: driving task performance (e.g., lane tracking, steering wheel movement), driving speed and distance monitoring, per- formance on surrogate tests (i.e., code substitution, critical tracking test, simple response vig- ilance test), continuous video monitoring, physiological measures as well as driver-supplied information (e.g., daily logs, Stanford Sleepiness Scale rating). A follow-up study focused on five groups of CMV drivers. One group of five drivers worked nights (i.e., 4 13-hr nights, followed by 36 hours off, and then worked 4 13-hr nights) and the remaining four groups worked days. Three of the groups worked 4 13-hr days and had varying recovery time (i.e., group 1: 10 to 11 hr, three drivers; group 2: 36 hr, six drivers; group 3: 60 hr, six drivers) before working an additional day. The final group of five drivers worked 4 13-hr days, had 36 hr off and worked 4 additional days. Scope of Work: Literature review. Field study involving Canadian and American CMV drivers. Sample Size: 80 male CMV drivers; 25 to 65 years old Industry Sector: CMV drivers Major Limitations: "The limitations of the study relate primarily to the lack of full control over the full range of conditions affecting alertness and fatigue and the inability to isolate some factors due

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90 to unavoidable confounding of variables, a consequence of the naturalistic approach to this study." Findings 1. Time of day was far more important than time on task or cumulative number of trips in predicting driver fatigue. 2. Drivers in the C3: Nighttime condition had the least amount of sleep of all the conditions. 3. "Night driving (e.g., from midnight to dawn) was associated with worse performance on four important criteria" (e.g., average lane tracking standard deviation, drowsiness, code substitution, and sleep length). 4. "There was some evidence of cumulative fatigue across days of driving. For example, performance on the Simple Response Vigilance Test declined during the last days of all four conditions." 5. Drivers had approximately 2.5 hr less sleep than the amount of sleep they identified as their ideal. 6. Drowsiness in Conditions C3: Nighttime and C4: Daystart was markedly greater during night driving. Of episodes of drowsiness during on-road driving, 82% occurred between 1900 and 0659. 7. The follow-up study found that based on a small sample of drivers, 36 hr recovery was insufficient for day or night drivers, but especially for night drivers. Findings Directly Related Note: All following quotes are from Wylie 1996. to HOS (include page references): Driver Fatigue/Alertness p. ES-8, "The strongest and most consistent factor influencing driver fatigue and alertness in this study was time of day." p. ES-9, "Night driving (e.g., from midnight to dawn) was associated with worse perfor- mance on four important criteria . . ." (i.e. average lane tracking standard deviation, drowsiness, code substitution and sleep length). p. ES-9, "There was some evidence of cumulative fatigue across days of driving. For exam- ple, performance on the Simple Response Vigilance Test declined during the last days of all four conditions." p. ES-10, "Overall, drivers obtained about 2 hours less time in bed and 2.5 hours less actual sleep than their reported "ideal" daily amount of sleep." (i.e., ideal = 7.2 hr; actual sleep during study = 5.2 hr). p. 4-23, "The overall pattern was characterized by the longest sleep times in Condition C1-10day and the shortest in Condition C3-12nightstart . . ." (Total sleep time for: C1- 10day = 5.4 hr; C3-13nightstart = 3.9 hr) p. 4-33, "The observed prevalence of drowsiness formed a distinct peak about 8 hours wide, spanning late evening until dawn, and a 16-hour trough." p. 4-32, "The prevalence of drowsiness in conditions C3-13nightstart and C4-13daystart was markedly greater during night driving." p. 4-42, "There was probably greater drowsiness in Condition C2-10rotating, trips 4 and 5, because the rotating schedule had caused these last trips, on average, to be driven through the night. Although disruption of circadian rhythms and cumulative fatigue prob- ably contributed, time of day appeared to be a major factor."

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91 Driver Duration p. ES-9, "Hours of driving (time-on-task) was not a strong or consistent predictor of observed fatigue." Driver Health No significant findings or assumptions concerning impact on health.