Great Barrier Reef and Torres Strait
- Great Barrier Reef pilotage fatigue risk assessment
- Fatigue study on coastal pilots
- The work practices of marine pilots
- Work schedules of Great Barrier Reef Pilots
- Impact on wives and families
- Work and Sleep patterns
- Implications for fatigue management
- Information for Interest
- Restricted access
On Tour analyses of the work and rest patterns of Great Barrier Reef pilots: implications for fatigue management
Results: PATTERNS OF ACTIVITY ASHORE DURING BREAKS
8.0 Sleep ashore between Assignments
During a tour of duty GBR pilots alternate between working on ships and spending time ashore resting between each assignment. Breaks ashore present the opportunity for pilots to recuperate from the previous pilotage and prepare themselves for the next assignment. This section provides some understanding of the sleep patterns during breaks and evaluates the type of sleep experienced prior to undertaking the next assignment.
8.1 Accommodation Type while ashore
Table 8.0 shows the frequency by which a particular type of accommodation is used when ashore during assignment breaks. Thirty-three percent of assignment breaks were spent in pilot accommodation with 28 percent and 30 percent spent at home and in hotels/motels, respectively. Thus 63 percent of breaks are spent in alternate accommodation. Pilots who reside at home during assignment breaks are those who live (in coastal towns in northern and central Queensland) in close proximity to the operational regions.
Table 8.0 Type of accommodation ashore between assignments
|
Location |
Percent |
|---|---|
| At home | 27.9 |
| Pilot accommodation | 33.3 |
| Hotel/motel | 30.0 |
| Other | 8.8 |
8.2 Total time in bed and sleep time per 24 hours
While ashore, most of the time pilots were in bed they were asleep (Figure 8.0). Table 8.1 reveals no shipping route effect on either total time in bed or total sleep time ashore. Total sleep time ashore ranged from 9 hours prior to GNE Channel assignments to 10 and 11 hours prior to work on Hydrographers Passage and the Inner Route, respectively (Table 8.1).
Figure 8.0 Mean total time in bed and total sleep time per 24 hours ashore, by shipping route
Table 8.1 Analysis of the total time in bed and total sleep time per 24 hours ashore, by shipping route (1) *
|
Effect |
Post hoc results |
Mean (sem) |
F Statistics |
p-value |
|---|---|---|---|---|
| Total time (hours) in bed per 24 hours
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
11.77 (1.20) 10.72 (1.24) 9.82 (0.81) |
0.93 |
= 0.399 |
| Total sleep time (hours) per 24 hours
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
10.99 (1.21) 10.06 (1.10) 9.27 (0.89) |
0.50 |
= 0.606 |
- Results of full two-way Analysis of Variance (ANOVA) model. p < 0.01 considered statistically significant. n/a = Post hoc testing not performed when main effects not significant
*Shipping route for ashore sleep data refers to the route of the next assignment
Shore sleep data assessed on 165 of 176 assignments – only for breaks of 3 days or less.
8.3 Duration of each sleep period and number of sleep periods per 24 hours
In terms of the total sleep duration per 24 hours pilots’ sleep approximated more conventional sleeping hours. This section provides some insight into the patterning of pilots sleep. Logbook data indicated while ashore, sleep was generally taken in one sleep period, (occasionally more than one) averaging 7 hours (Figure 8.1). Neither the duration nor number of sleep periods differed displayed a shipping route effect (Table 8.2). This result indicated that total sleep ashore of between 9 and 11 hours consisted of one sleep of approximately 7 hours with an additional sleep of 2-3 hours. Given that pilots often undertake travel between ports during assignment breaks the additional short sleep period may be related to travel and/or the timing of sleep across the break.
Figure 8.1 Mean duration of each sleep period and number of sleep periods per 24 hours ashore, by shipping route
Table 8.2 Analysis of the duration of each sleep period and the number of sleep periods per 24 hours ashore, by shipping route (1) *
|
Effect |
Post hoc results |
Mean (sem) |
F Statistics |
p-value |
|---|---|---|---|---|
| Duration (hours) of each sleep period
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
6.60 (0.17) 7.06 (0.36) 6.42 (0.44) |
0.17 |
=0.847 |
| No. of sleep periods per 24 hours
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
1.66 (0.13) 1.48 (0.18) 1.40 (0.18) |
0.87 |
=0.462 |
- Results of full two-way Analysis of Variance (ANOVA) model. p < 0.01 considered statistically significant. n/a = Post hoc testing not performed when main effects not significant
*Shipping route for ashore sleep data refers to the route of the next assignment
Shore sleep data assessed on 165 of 176 assignments – only for breaks of 3 days or less.
8.4 Other sleep characteristics associated with Fatigue
A further understanding of fatigue levels was provided by the analysis of data on the time taken to fall asleep (sleep latency) and the time to feel alert. Sleep latency ranged between 6 and 8 minutes and was similar prior to assignments on the three shipping routes (Table 8.3).
Further analysis showed a similar proportion of sleep prior to assignments with latencies under 5 minutes on the three shipping routes. That a considerable percent of this sleep approximated a fatigued state suggested, despite sleeping out of normal physiological sleeping times and in alternate accommodation, pilots were tired and fell asleep quickly.
Table 8.3 also reveals that while ashore pilots took between 9 and 17 minutes to feel alert. This figure was double the time taken to feel alert at sea.
The relatively high sleep efficiency scores of 93 percent (Table 8.3) are consistent with data above indicating that most of the time pilots were in bed, they were asleep (Table 8.0). That 63 percent of breaks were spent in alternate accommodation may have contributed to pilots losing between 7 and 10 minutes of sleep due to awakenings (Table 8.3).
Table 8.3 Analysis of other sleep characteristics associated with fatigue ashore, by shipping route (1) *
|
Effect |
Post hoc results |
Mean (sem) |
F Statistics |
p-value |
|---|---|---|---|---|
| Sleep latency (mins)
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
7.80 (0.91) 6.62 (1.12) 5.65 (1.11) |
0.10 |
=0.905 |
| Time (mins) to feel alert
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
15.14 (5.11) 9.08 (3.43) 17.23 (6.07) |
0.39 |
= 0.674 |
| Percent of sleep periods with sleep latency < 5 mins
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
37.11(2.84) 42.59 (6.79) 52.77 (7.61) |
1.0 |
=0.369 |
| Time (mins) lost due to awakenings
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
6.71 (0.81) 10.29 (2.02) 7.47 (2.65) |
0.31 |
= 0.733 |
| Sleep efficiency
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
92.50 (0.64) 93.78 (1.06) 93.91 (2.58) |
0.69 |
= 0.504 |
- Results of full two-way Analysis of Variance (ANOVA) model. p < 0.01 considered statistically significant. n/a = Post hoc testing not performed when main effects not significan
* Shipping route for ashore sleep data refers to the route of the next assignment
Shore sleep data assessed on 165 of 176 assignments – only for breaks of 3 days or less.
8.5 Timing of sleep
From the results thus far while ashore, pilots' sleep approximates normal sleeping habits in terms of the total sleep and patterning. However, sleep timing ashore and therefore its duration and potential recuperative value is determined by the starting times of breaks. Given that earlier sections revealed that the starting times of breaks ashore displayed a fairly rectangular distribution across the 24 hour cycle a closer examination of logbook data on the percent of sleep during optimal hours (2200-0800) was undertaken.
8.5.1 Percent of sleep inside 2200-0800 hours
Approximately 83 percent of sleep was within this time during breaks prior to Hydrographers Passage assignments, with 73 percent of sleep meeting this criteria prior to work on the Inner Route and GNE Channel (Figure 8.2). There was no significant shipping route effect (Table 8.4). Conversely, these findings also indicated that between 20 and 30 percent of sleep was outside optimal hours prior to work on the three shipping routes. These data suggested that during a percentage of breaks the duration and/or timing of the break did not allow for sleep to occur during optimal sleeping periods. Thus sleep may not provide sufficient recuperative value to diminish fatigue accumulated during work at sea.
The distribution of sleep starting times (Figure 8.3) shows that 60-70 percent of sleep ashore began between the hours of 2000 and midnight prior to assignments on each of the shipping routes; the remainder of sleep periods were fairly evenly distributed between midnight and 2000.
Figure 8.2 Mean percent of sleep inside 2200-0800 ashore, by shipping route
Table 8.4 Analysis of the percent of sleep periods inside 2200-0800 ashore, by shipping route(1) *
|
Effect |
Post hoc results |
Mean (sem) |
F Statistics |
p-value |
|---|---|---|---|---|
| Percent of sleep inside 2200-0800
Inner Route Hydrographers Passage GNE Channel |
n/a n/a n/a |
73.55 (2.44) 81.35 (4.74) 72.41 (6.28) |
0.21 |
= 0.810 |
- Results of full two-way Analysis of Variance (ANOVA) model. p < 0.01 considered statistically significant. n/a = Post hoc testing not performed when main effects not significant
* Shipping route for ashore sleep data refers to the route of the next assignment
Shore sleep data assessed on 165 of 176 assignments – only for breaks of 3 days or less
Figure 8.3 Frequency distribution - starting times of sleep ashore, by shipping route.
8.6 Sleep Quality
Sleep quality ashore was determined using identical procedures to those described for assessing sleep quality at sea (Section 7.6). As Figure 8.4 shows sleep quality ratings ranged between 19 and 22 and were towards the higher end of the sleep quality scale (range 5-25). The significant shipping route differences in sleep quality related to the higher sleep quality reported prior to Inner Route assignments, compared with sleep quality values prior to work on the other two shipping routes (Table 8.5). There is a possibility that the higher sleep quality scores indicated sleep ashore was recuperative; however, that between 20-30 percent of this sleep is opposed to normal physiological sleeping times and taken in pilot accommodation and hotels raised some doubt over the validity of the high sleep quality ratings. As with sleep quality at sea, it is likely that sleep quality was over rated.
Figure 8.4 Sleep quality ratings ashore, by shipping route
Table 8.5 Analysis of sleep quality ratings ashore, by shipping route1 *
|
Effect |
Post hoc results (2) |
Mean (sem) |
F Statistics |
p-value |
|---|---|---|---|---|
| Rating of sleep quality
Inner Route Hydrographers Passage GNE Channel |
1 2 2 |
22.37(0.18) 21.18(0.55) 19.72(0.61) |
5.89 |
=0.003 |
- Results of full two-way Analysis of Variance (ANOVA) model. p < 0.01 considered statistically significant.
- Results of Tukey’s Studentised Range test for post-hoc differences (Type 1 Error Rate = .01) p < 0.01 for differences between shipping routes from post-hoc
* Shipping route for ashore sleep data refers to the route of the next assignment
Shore sleep data assessed on 165 of 176 assignments – only for breaks of 3 days or less
last updated: October 1998