This is the third report in a series describing research aimed at developing better models of work-rest schedules that have demonstrated effectiveness for managing fatigue. The ultimate purpose of these studies is to support the development of alternative compliance approaches to the regulation of working hours. Rather than attempting to estimate the effectiveness of alternative work-rest schedules by applying theoretical knowledge of the area of fatigue, these studies have actually measured fatigue on-road under a range of different work-rest schedules.
This report describes an evaluation of the first pilot Fatigue Management Programme allowed under the Queensland Department of Transport alternative compliance programme. This alternative work-rest schedule differed from the regulated regime in that it allowed longer periods of active work without rest (6 hours instead of 5 hours) and allowed the mandatory six hours of continuous rest to be taken in two parts instead of one.
The results of the evaluation cast some doubts on the effectiveness of the alternative work-rest schedule and suggest that the balance between work and rest in the schedule needs to be re-examined. Although reported fatigue levels were not particularly high at any time in the study period, reaction speed became significantly slower on both laptop and palmtop versions of the Simple Reaction Time test across the study period. Furthermore, the results showed that reaction speed at the end of the study period had slowed to be poorer than the performance level found in drivers at 0.05% BAC. For the Mackworth Clock Vigilance test, performance also showed deterioration over the study period and showed some evidence of being poorer than the alcohol standardised performance at 0.05%BAC on occasions across the study period. For both tests, performance had deteriorated sufficiently to constitute a safety risk based on the community-accepted standard for on-road performance.
The results of the evaluation provide some hints about what aspects of the work-rest schedule needs to be changed. Drivers who did most work in this schedule rated themselves the most tired. This was also found in the first regulated regime evaluation (Williamson, Feyer, Finlay-Brown, & Friswell, in press, CR190) and consequently provides further evidence that long working hours are a serious risk factor for the experience of fatigue in driving
Most significantly, the length and quality of sleep and the number of breaks seem to be the major problems in this roster. The results show that the drivers who derived least benefit from their last rest were most likely to suffer effects on their capacity to perform. Many of the measures showed little or no improvement even after a sleep break, especially towards the end of the study period, suggesting a problem with either the positioning and/or the length of the breaks. This pattern was also seen in the simulated FMP evaluation described in the second report of the series (Williamson et al., in press, CR190) where by the second day of an extended work period (16 hours) breaks became increasingly useless in producing recovery of performance. Clearly, there needs to be a balance between the amount of work and the amount of rest needed to allow for proper recovery.
Not only is the length of break important, but the results also suggest that the quality of sleep obtained in the break is important. Drivers in this study were on-road for around twice as long as in the previous evaluations. It is likely that on-road rest is of inferior quality to rest obtained at home. This may be one of the reasons for the performance effects seen in this study. If this is the case, one of the suggested targets for improving this FMP schedule would be to reduce the amount of time away from home.
This report also describes a second evaluation of the current working hours regulations for managing fatigue. A similar evaluation was described in the second report (Williamson et al., in press, CR190) in which drivers were studied from the beginning of a period of days of work after at least a 24 hour break, for the period until their next 24 hour break. The current study was a replication of the first in a different company in which the working hours regulations are implemented slightly differently. Unlike the first evaluation, where drivers tended to work from a main company depot so that trips started and ended in the same place, in this second company, drivers were based considerable distances away from the company depot. This meant that the study was more difficult to organise and that many drivers in the study had been driving for a substantial period when they began the study so making it difficult to estimate fatigue and performance levels from maximally rested drivers.
Nevertheless, the results of the second working hours evaluation showed the same as the first one. The results showed no evidence of significant increases in fatigue or deterioration in performance capacity over a selected period of work. Fatigue ratings showed only minor, non-significant changes from the beginning of the study period across the first work period for the remainder of the study period. Similarly, Simple Reaction Time and Mackworth Clock Vigilance test measures also showed only slight changes across the study milestones. These results need to be interpreted with some caution, however. For many drivers in the study, it was not possible to measure their performance when they were maximally rested. This means that the lack of change over the study period may have been because drivers were tired on both occasions. Using the alcohol performance standards, however, it was possible to conclude that performance was within the estimated performance standard for most drivers so suggesting that the roster is allowing adequate rest to balance work.
Like the previous evaluation, however, this study showed that long periods of work, inadequate breaks and poor quality sleep will produce adverse effects on performance. Drivers who did the longest working hours and especially night work showed the slowed reaction time in the Simple Reaction Time test. Similarly, where drivers had fewer breaks or poorer quality sleep in their breaks, their ability to maintain consistent and accurate performance on the Mackworth Clock Vigilance test was adversely affected.
These studies have reinforced again the usefulness of taking this evaluation
and model-building approach to the problem of fatigue management in the long
distance road transport industry. The techniques developed for the approach
have demonstrated their usefulness for detecting fatigue effects in this study
as well as the previous ones. The results have reinforced the conclusions of
the earlier evaluation of the current working hours regime by showing that there
appear to be no major effects of fatigue. They show, however, that where drivers
work to the upper limits of the current regime, the risk of fatigue effects
are significantly increased. The results also demonstrate the problems of an
alternative compliance approach to fatigue management and point out the general
areas for improvement in the work-rest schedule.
Download Complete Document: Duty_Time_1 [PDF: 856 KB]
Type: Research and Analysis Report
Sub Type: Consultant Report
Author(s): A Williamson, A-M Feyer, R Friswell, S Finlay Brown
ISBN: 0 642 25579 2
Topics: Fatality, Heavy vehicle
Publication Date: 01/06/00