An analysis of the work schedules of Great Barrier Reef pilots

Results and Discussion

Within the Great Barrier Reef – Torres Strait region, there are three main shipping routes transited by pilots. Hydrographers Passage is located east of Mackay, the Inner Route runs parallel to the Queensland coastline while the Great North East Channel extends north east from Cape York. The characteristics of each route vary considerably in terms of transit times, navigational hazards and travel requirements. Hence, as part of the overall fatigue focus of the study, it was deemed important to assess the potential fatigue aspects associated with the main shipping routes transited by Great Barrier Reef pilots.

6.1 Number Of Work Assignments

Figure 6.0 shows the mean number of assignments for each of the shipping routes. Across the 18 month period, 2987 Inner Route, 862 Hydrographers Passage and 445 Great North East Channel assignments were performed. Comparisons made on the basis of the Poisson model indicated significant between route differences existed (p < 0.01). Based on mean figures, it is evident that approximately 70, 20 and 10 percent of pilotage work performed in the Great Barrier Reef – Torres Strait region was conducted on the Inner Route, Hydrographers Passage and the Great North East Channel respectively. Hence, Inner Route assignments constitute the main source of work for Great Barrier Reef pilots.

Figure 6.0 Mean number of work assignments, by shipping route

95% Confidence intervals for each route were:

Inner Route: 2880-3094; Hydrographers: 804.5-919.5; Great North East: 403.6-486.3

6.2 Duration of Work Assignments

Figure 6.1 presents the mean duration of work assignments (ship time) for each of the shipping routes while Table 6.0 summarises the analysis of shipping route differences in this data. Assignments on the Inner Route were significantly longer (55.65 hours) compared with assignments on Hydrographers Passage (12.08 hours) and the Great North East Channel (14.64 hours), which were similar. Although not shown, frequency distributions seemed to confirm these results as over 95% of Inner Route assignments were longer than 30 hours in duration, approximately 95% of Hydrographers Passage assignments were between 10 and 15 hours duration and approximately 90% of Great North East Channel voyages were between 9 and 20 hours in duration. These findings reflect the transit distances associated with each route. As a consequence of the differences in average assignment duration between shipping routes, it would seem important to consider the differences between shipping routes when assessing and managing potential fatigue.

Figure 6.1 Mean duration (hours) of work assignments (ship time) by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.0 Analysis of the mean duration (hours) of work assignments (ship time) by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

6.3 Duration of Breaks between Work Assignments

Figure 6.2 shows the mean duration of breaks between assignments (non-ship time) by shipping route, while Table 6.1 presents a summary of the analysis of this data in terms of shipping route differences. Breaks between voyages on Hydrographers Passage were significantly shorter (46.32 hours) compared with assignments on the Inner Route (51.6 hours) and Great North East Channel (53.04 hours).

When presenting this data in frequency distribution format (Figure 6.3), it can be noted that for all three shipping routes, the majority of assignments were interspersed by breaks of 24 hours or more. Thus, current minimum rest break regulations are being met in most instances. However, a small percentage of rest breaks failed to meet regulations which state a minimum of 24 hours rest before Inner Route passages and 12 hours for Hydrographers Passage and Great North East Channel voyages. In light of the heightened fatigue potential associated with inadequate rest between work periods, closer monitoring of rest breaks may be warranted.

Figure 6.2 Mean duration (hours) of breaks between work assignments (non-ship time) by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.1 Analysis of the mean duration (hours) of breaks between work assignments (non-ship time) by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

Figure 6.3 Frequency distribution - Duration of breaks between work assignments by shipping route

6.4 Percent of the Work Assignment Performed at Night

Given the additional demands associated with night work (refer to section 5.11) an assessment of the percent of assignment time (ship time) undertaken at night (defined as between 1818 and 0525 hours) on each shipping route was conducted. Figure 6.4 shows this data for each shipping route separately, while Table 6.2 presents a summary of the analysis of shipping route differences in this data. There were significant differences between each of the shipping routes, with a greater percentage of Inner Route assignments being performed at night (57.33%), followed by assignments on the Great North East Channel (47.0%) and then assignments on Hydrographers Passage (43.6%). This pattern in the results may be related to the transit time associated with each route as the longer the work assignment is, the greater the probability that night work will be incurred. Figure 6.5 clearly shows that the majority of Inner Route assignments involved between 40 and 70% of night work.

That Inner Route assignments are significantly longer in duration (Table 6.0) and involve greater amounts of night work (Table 6.2) indicates that there may be a heightened risk of fatigue development associated with this route. The potential importance of this finding is enhanced when viewed in combination with the fact that Inner Route assignments constitute the main source of pilotage work in the Great Barrier Reef – Torres Strait region (Figure 6.0).

To optimise the potential for sleep at sea, the possibility of charting alternative shipping channels should be examined. For example, pilots have commented that the use of the Fairway Channel region of the Inner Route would eliminate one of the most difficult sections of this route and permit more extensive rest and sleep periods (Personal Communication – Pilot Advisory Group, 18 May 1998). At present, the channel has been surveyed but no charts or Differential Global Position (DGP) facilities for this region have been developed.

Figure 6.4 Percent of assignment (ship time) performed at night by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.2 Analysis of the mean percent of assignments (ship time) performed at night, by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

Figure 6.5 Frequency distribution - Percent of assignment (ship time) performed at night by shipping route

6.5 Starting Times of Work Assignments

Figure 6.6 shows the mean starting times of work assignments conducted on each shipping route. A summary of the analysis of shipping route differences in this data is presented in Table 6.3. While significant differences between the shipping routes in mean starting times of assignments existed, post hoc testing failed to identify the source of these differences. However, it can be noted from data within table 6.3 that Inner Route assignments (12:16) began approximately 45 to 50 minutes later than Hydrographers Passage (11:25) and Great North East Channel assignments (11:23).

As depicted by Figure 6.7, starting times were fairly evenly distributed over the 24 hour cycle, with around 15 to 20% of work assignments beginning in each 4 hour time period. As a consequence of this even distribution over the 24 hour cycle, when results are averaged a mean starting time of approximately 1200 hours was obtained.

Figure 6.6 Mean starting times of work assignments by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.3 A summary of the analysis of the starting times of work assignments, by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

Figure 6.7 Frequency distribution - Starting times of work assignments by shipping route

6.6 Starting Times of Breaks between Work Assignments

The average starting times of rest breaks between work assignments (non-ship time) for each shipping route are presented in Figure 6.8, while Table 6.4 summarises the analysis of shipping route differences in this data. Mean starting times of rest breaks around 1200 hours were recorded for all three shipping routes. This is once again attributable to the fairly even distribution of the starting times for rest breaks across the 24 hour cycle as depicted by Figure 6.9.

Figure 6.8 Mean starting times of breaks between work assignments by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.4 Analysis of the mean starting times of breaks between work assignments, by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01) n/a Post hoc testing not performed when main effects not significant.

Figure 6.9 Frequency distribution - Starting times of breaks between work assignments by shipping route

6.7 Travel To and From Ships Per Work Assignment

To determine whether any one particular shipping route may be associated with greater amounts of travel, an assessment of the travel duration to and from ships per work assignment for each shipping route was performed. Figure 6.10 presents this data for each shipping route separately, while Table 6.5 summarises the analysis of shipping route differences in this data. There were significant differences, with mean travel to and from assignments on the Great North East channel (3.24 hours) being greatest, followed by travel to and from Inner Route assignments (2.53 hours) and then travel to and from Hydrographers Passage assignments (2.38 hours). Figure 6.11 appears to confirm these results as while 100% of assignments on Hydrographers Passage and approximately 98% on the Inner Route involved 4 hours or less of travel, only 75% of assignments on the Great North East Channel had similar travel hours. The remaining 25% of Great North East Channel assignments involved between 4 and 8 hours of travelling to and from ships.

These results reflect the accessibility of boarding grounds associated with each route and the mode of transport used. For example, the remote location of boarding grounds for the Great North East Channel and the tendency to use launch vessels contributes to the longer duration of travel associated with this route. On the other hand, many of the boarding grounds for the Inner Route and Hydrographers Passage are located closer to shore, and in those instances when significant distances need to be travelled, helicopters are often used.

Figure 6.10 Mean duration of travel to and from ships per work assignment by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.5 A summary of the analysis of the mean duration of travel to and from ships per work assignment by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

Figure 6.11 Frequency distribution - Duration of travel to and from ships per work assignment by shipping route.

6.8 Number of Potential Sleep Periods (2200-0800 hours) in Breaks between Work Assignments

As noted earlier in the report, when sleep is taken between the hours of 2300 and 0700 the recuperative value of the recovery period tends to be greatest. To assess whether differences between shipping routes existed in terms of opportunity to achieve optimal sleep, an assessment of the number of times pilots were potentially able to obtain an uninterrupted period of sleep between 2200 and 0800 hours during rest breaks prior to assignments on each shipping route was undertaken.

Figure 6.12 shows the number of potential sleep periods between 2200 and 0800 hours in breaks between assignments for each shipping route. Table 6.6 summarises the analysis of shipping route differences in this data. Significant differences were evident, with breaks before Inner Route (1.75 potential opportunities) and Great North East Channel (1.81 potential opportunities) assignments potentially allowing pilots more opportunity to achieve a full sleep period between 2200 and 0800 hours, compared with breaks prior to voyages on Hydrographers Passage (1.53 potential opportunities).

Contributing to this finding is the fact that on average, rest breaks prior to Hydrographer Passage assignments are significantly shorter than breaks prior to assignments on either of the other two routes (Table 6.1).

While present regulations stipulate the minimum duration of rest breaks prior to work assignments (AMSA 1997), these regulations do not consider the timing of breaks across the 24 hour cycle. Given that this issue appears to have a considerable impact on the recuperative value of breaks and hence the fatigue status of the employee, reassessment of the present regulations may be warranted.

Figure 6.13 clearly indicates that on all shipping routes, most rest breaks prior to assignments present pilots with at least one potential opportunity to achieve an 8 hour block of sleep between the hours of 2200 and 0800. However, in approximately 12% of breaks preceding Inner Route assignments, 14% prior to Great North East Channel assignments and 22% before Hydrographers Passage assignments, no opportunity for an uninterrupted period of sleep between normal sleeping hours (i.e. 2200 and 0800 hours) was available. This does not indicate that pilots were unable to achieve any sleep during the rest period. Rather, it highlights that in a number of instances sleep during rest breaks was sub-optimal in terms of its circadian placement. As a consequence, the recuperative value of the pilot’s sleep would have been compromised leading to a heightened risk of fatigue and performance decrements. While it may be argued by some that marine pilots adjust to fragmented and displaced sleep, circadian adaptation to work schedules involving continual changes in work and rest times has not been evidenced in the literature (Colquhoun 1985; Colquhoun et al. 1987; Knauth & Rutenfranz 1976).

Figure 6.12 Mean number of potential sleep periods (2200-0800 hours) in breaks between work assignments by shipping route

Note: Data analysis based on n values shown in Methods (Section 3.2).

Table 6.6 Analysis of the mean number of potential sleep periods (2200-0800 hours) in breaks between work assignments by shipping route (1)

1. Results of full two-way analysis of variance (ANOVA) model. p < 0.01 considered statistically significant.
2. Results of Tukey’s Studentised Range Test for post-hoc differences (Type I Experimental Error Rate = .01).

Figure 6.13 Frequency distribution - Number of potential sleep periods (2200-0800 hours) in breaks between work assignments by shipping route

6.9 Summary

The analysis of shipping routes highlighted that over the 18 month period, approximately 70 percent of pilotage work in the Great Barrier Reef – Torres Strait region was performed on the Inner Route. This shipping route was also associated with significantly longer transit times and involved a greater percentage of night work, and hence, may be associated with an increased risk of fatigue development.

Breaks between assignments were significantly shorter between assignments on Hydrographers Passage and significantly more travel to and from ships was incurred on the Great North East Channel. Additionally, it was identified that on all three shipping routes, approximately 12-20% of rest breaks between assignments failed to provide the opportunity for uninterrupted sleep between 2200 and 0800 hours. On all three routes, starting times of assignments and breaks were fairly evenly distributed across the 24 hour cycle, thereby highlighting the irregularity associated with pilotage work.

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