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Our tour analyses of the work and rest patterns of Great Barrier Reef pilots: implications for fatigue management

Summary of Results

This investigation represents the final phase of a comprehensive research program designed to investigate the contributing factors to fatigue in the work practices of Great Barrier Reef (GBR) pilots. In this study information related to both general and specific aspects of the work and rest periods was recorded by pilots in specially designed logbooks. The information evaluated focused on factors which have the potential to produce fatigue and decrements in performance and included the timing and quality of sleep during assignments at sea and during rest breaks, and estimates of fluctuations in alertness during work on the bridge. Additional work specific factors which may increase the difficulty of an assignment and have a bearing on fatigue were also assessed. These included the weather, ship handling and under keel clearance, bridge team skill levels and accommodation and meals.

Specific patterns of sleep at sea and ashore that have the potential to reduce the recuperative value of sleep such as duration and timing across the 24 hour cycle, and the percentage of sleep during optimal physiological sleeping hours (2200-0800) were also examined.

The results are based on an analysis of 176 work assignments undertaken on 3 shipping routes by 23 GBR pilots during the months of May and June, 1998. In general the results identified a range of work/rest, alertness, personal and environmental factors that potentiate or predispose pilots to fatigue.

Overview of Work Assignments

Work assignments involve a continuous period of time spent by pilots onboard vessels: assignment duration is adjusted for travel to and from the ship. In the Barrier Reef region pilotage work involves pilots alternating between work assignments on the ship and time ashore during assignment breaks. This section provides an overview of work assignments in terms of the duration, starting times and the amount of time spent on pilotage duties. Additionally, the degree of contribution to work assignment stress and/or fatigue from pilotage specific factors was examined.

Inner Route assignments averaged 54 hours compared with 14 and 16 hours for pilotages on the GNE Channel and Hydrographers Passage, respectively.
Ninety-five percent of time on board ship was spent on pilotage duties on the Inner Route and GNE Channel, compared with 66 percent on Hydrographers Passage assignments. Pilotage duties are defined as duties undertaken during the time between beginning and ceasing pilotage and cover bridgework and rest periods.
During Inner Route and GNE Channel passages, the percentage of time spent on pilotage duties resulted in a ratio of pilotage time to non pilotage time of 19:1. On Hydrographers Passage assignments this ratio was 2:1.
During a tour (period of time during which a number of individual work assignments are completed) onboard time accounts for 43 percent of the tour time with 57 percent being ashore time, thus the onboard to ashore ratio was1:1.32.
The irregularity of pilotage work was confirmed by the rectangular distribution of assignment and break starting times across the 24 hour cycle on all shipping routes.
Inner Route and GNE Channel assignments were rated more fatiguing than work on Hydrographers Passage.
Difficulties associated with weather conditions, visibility, ship handling and under keel clearance, bridge team skill levels, meals and accommodation were perceived by pilots to be more problematic on the Inner Route and GNE Channel.
Travel to and from ships was the highest rated of the factors contributing to work assignment stress and fatigue on the three shipping routes.

Bridgework

While the previous work schedule analysis provided details of the duration of work and rest periods, the logbook data provided an opportunity to record specific details of bridgework (defined as time on the bridge). These included details of bridgework such as the duration, timing and the percent undertaken at night and during critical hours which are summarised below.

During an assignment, the mean duration of bridge periods totalled 21 hours on the Inner Route and 7 and 9 hours for Hydrographers Passage and the GNE Channel, respectively.
On Inner Route assignments, bridge periods averaged 3 hours and were undertaken during 7 separate periods. Whereas on other shipping routes bridge periods averaged 6.6 hours and were conducted during a single bridge period.
For GNE Channel and Hydrographers Passage assignments, 98 percent and 86 percent of pilotage time (defined as the time between commencing and ceasing pilotage duties during an assignment) was spent on the bridge. In contrast, 51 percent of pilotage time was spent on the bridge on the longer Inner Route.
On the three shipping routes, the percentage of bridge time at night, that is, between 1818 - 0525 hrs, was similar: Inner Route, 46 percent; Hydrographers Passage, 37 percent; and GNE Channel, 52 percent.
Across the three shipping routes, approximately 30 percent of bridge times were undertaken during critical hours (2300-0600), which has been shown to be associated with reduced alertness and increased accident risk.
During the sampling period, sea conditions during bridge periods were predominantly medium on the GNE Channel and calm/medium on the other two routes.

Sleep at Sea

During pilotage work, sleep at sea is usually taken during the less difficult navigational sections of the route where pilots consider the ships progress can be safely monitored by the bridge team. Information on the duration, quality and timing of sleep during an assignment was recorded by pilots and analysed to identify any differences between the 3 shipping routes. The results of these analyses are provided below.

During assignments total sleep time per 24 hours averaged 0.6 hours on the GNE Channel and 4 and 5 hours on Hydrographers Passage and the Inner Route, respectively.
During Inner Route assignments the 5 hours of sleep per 24 hours was undertaken in approximately two, 2.5-hour periods. In contrast, on Hydrographers Passage and GNE Channel pilotages, average daily sleep was taken during a single period. Pilots reported losing between 2 and 3 minutes of sleep due to awakenings.
Sleep latency (time to fall asleep) ranged between 4 and 7 minutes at sea and was within or close to sleep latency periods associated with a fatigued state (latency < 5 minutes). Fatigue is considered a general response to various forms of stress resulting in performance decrements.
The percentage of sleep with latencies < 5 minutes was: 32 percent on Hydrographers Passage, 39 percent on the Inner Route and 83 percent on the GNE Channel.
Sleep efficiency (percent of time in bed spent sleeping) ranged between 90 and 93 percent and indicated pilots were exhausted, and slept with very few interruptions despite sub-optimal sleeping accommodation in some instances.
Sleep quality was similar on all three shipping routes, with scores of between 19 to 21, towards the higher end of the scale (range 5-25) and similar to ratings of sleep quality reported by mariners involved in day work.
The percent of sleep taken during the optimal hours of 2200-0800 differed according to the shipping route. On Hydrographers Passage, 81 percent of sleep was within this time, whereas 50 and 60 percent of sleep was between these hours on the Inner Route and GNE Channel, respectively. Thus, between 40 and 50 percent of sleep was outside optimal sleeping times for the Inner Route and GNE Channel.
Daily sleep debt (difference between sleep duration ashore and at sea) averaged 5.7 hours for the Inner Route and was more problematic on this route given the 55 hour assignment duration in this region.
During sleep periods predominantly calm sea conditions were experienced on Hydrographers Passage. For the Inner Route calm or medium conditions prevailed during 50 percent of sleep periods; in contrast on GNE Channel assignments sea conditions were principally medium.

Sleep ashore

Breaks between assignments provide an opportunity for pilots to recuperate and prepare for the next assignment. Depending on the distance between the point of embarkation and the pilot's home base, pilots spend their break in company accommodation or at home. An assessment of sleep patterns during breaks ashore provided an insight into the recuperative value of these periods.

Thirty-three percent of breaks were spent in pilot accommodation, and others spent at home (28 percent) and in hotels/motels (30 percent), with around 10 percent in other types of accommodation.
Average break duration before assignments ranged from 36 hours for Hydrographers Passage to 60 and 72 hours for GNE Channel and Inner Route passages, respectively.
Between 5 and 10 percent of assignment breaks did not comply with current guidelines for break duration.
Total sleep time per 24 hours before assignments on the Inner Route, Hydrographers Passage and GNE Channel was 11, 10 and 9 hours, respectively.
Prior to assignments on each shipping route, sleep ashore approximated conventional patterns; that is, sleep was mostly taken in one sleep period averaging 7 hours plus an additional shorter period of 2-3 hours.
Pilots averaged between 5 and 8 minutes to fall asleep ashore, with 39 percent of sleep periods displaying latencies of less than 5 minutes.
While sleeping ashore pilots lost between 5 and 7 minutes due to awakenings, and reported taking between 9 and 17 minutes to feel alert.
Approximately 20-30 percent of sleep began outside the optimal sleeping hours (2200-0800). This finding indicates that break duration and/or timing prevented sleep being taken during optimal hours during a number of breaks.
Sleep quality ashore was rated relatively high, with scores between 19-22 similar to sleep quality ratings at sea. Thus, relatively high ratings of sleep quality applied to the longer duration sleep ashore and the shorter sleep at sea.

Measures of Alertness and Fatigue during bridge periods

Alertness fluctuations and the presence of fatigue symptoms during bridgework have been associated with decreased performance and increased accident risk. A summary of alertness ratings and the presence of fatigue symptoms during bridge periods are presented below.

Pilots average alertness ratings during bridge periods ranged between 6.1 and 7.7 and were towards the upper end of the rating scale (scale 1-9). There were no significant differences in alertness ratings during bridgework across the shipping routes or changes across time.
The percentage of bridge periods with alertness ratings < 3 (indicating sleepiness) ranged from 3 percent on Hydrographers Passage to 8 and 12 percent on the Inner Route and GNE Channel, respectively.
The number and frequency of fatigue symptoms was significantly greater for bridge periods on the Inner Route and GNE Channel assignments compared with Hydrographers Passage. This finding is consistent with a reduction in the degree of difficulty associated with pilotage work on Hydrographers Passage.
The percentage of bridge periods exhibiting one or more symptoms of fatigue ranged from 58 percent for the Inner Route and Hydrographers Passage to 83 percent for GNE Channel work assignments.
The presence of acute fatigue was identified by the considerable proportion of sleep episodes with latencies of less than 5 minutes and some bridge periods with minimum alertness.

Factors associated with high fatigue levels and low alertness levels on the bridge

Results from the analysis of logbooks and other data sources, particularly the work schedules (Parker et al., Report No 2, 1998) indicated the presence of several key measures associated with decreased alertness and increased fatigue. In light of these findings, a series of multiple linear regression models were used to assess contributions to variation in mean overall fatigue, stress, and minimum alertness measures of pilot data reflecting ashore and at-sea variables.

Over 90 percent of the variation in the three outcome variables of fatigue, stress and alertness was accounted for by individual differences in pilots and total break and work assignment duration.
More specifically, modelling procedures indicated that break duration contributed relatively more to alertness than to fatigue and stress. In contrast, assignment duration contributed relatively more to fatigue and stress than to alertness. Although the contribution was small, results suggested that the total duration of bridge periods per assignment contributed relatively more to alertness than to fatigue or stress.
Results of the modelling procedures indicated that if additional data were collected to enhance the present reporting system for evaluating fatigue, stress and alertness on the bridge it should consider both the total duration of bridge periods and duration during critical hours and travel to and from the ship.

Summary

Overall, the findings have indicated a presence of, and/or potential for, fatigue in the work practices of GBR pilots. The strong statistical evidence of a shipping route effect on characteristics of work assignments, bridgework and sleep at sea highlighted the different level of demands from work patterns on the three shipping routes. In addition, ship characteristics and environmental factors were more problematic on the Inner Route and GNE Channel pilotages, whereas travel impacted similarly on assignment stress and/or fatigue on all shipping routes.

The intensive nature of pilotage work at sea was reflected in the large percentage of work assignment time spent on pilotage duties. Pilots rated their average alertness during bridgework as quite high. This was surprising considering that a significant proportion of bridgework was undertaken during night and early morning hours. Moreover, up to 12 percent of bridge periods displayed alertness ratings indicating sleepiness, and a number of fatigue symptoms were experienced during bridgework on the Inner Route and GNE Channel.

Preliminary results of statistical modelling procedures highlighted the need to include data on work assignment and break duration, the total duration of bridge periods, bridge time during critical hours and work-related travel when evaluating the potential for fatigue, stress and alertness on the bridge.

Sleep at sea was short and mostly fragmented. Sleeping patterns at sea were interspersed by sleep ashore which approached more conventional sleeping habits in terms of the duration during a single sleep period. That a considerable percentage of sleep in both locations was outside optimal sleeping hours raised questions over the recuperative value of the sleep at sea and ashore. Several characteristics of sleep in both locations displayed a heightened potential for fatigue. For instance, the relatively high percentage of sleep with short sleep latencies and high sleep efficiency suggested a fatigued state.

That sleep quality was rated high at sea and ashore suggests that pilots sleep was recuperative, however, based on previous evidence from the same group, the high rating in both locations also suggested that sleep quality may have been slightly overrated by respondents. Given the considerable number of measures associated with work and sleep periods the possible over rating of these measures is unlikely to impact on the overall findings.

In summary, the findings from this investigation support those from earlier phases of the research program and indicate the presence of several critical factors associated with the work practices of GBR pilots which have the potential to contribute to both acute and chronic fatigue. When considered in the context of evidence of a significant relationship between fatigue and vessel and personal accidents which exists in the research literature, this information highlights the inadequacies of the current system used by AMSA and the pilot companies to monitor fatigue and the lack of any fatigue management program. In this respect, all groups responsible for the delivery of pilotage services in this most sensitive region are highly vulnerable to the consequences of fatigue, including decreased performance and increased accident risk. Consequently, the findings from this research have been used as the basis for the recommendations in this report which are designed to enhance existing work practices in the context of fatigue reduction through appropriate fatigue management strategies.

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last updated: October 1998