The work practices of Marine Pilots: a review

6.0 STRESS, FATIGUE AND PERFORMANCE

Essentially there are two ways in which an individual can respond to a potentially stressful situation. Either additional resources can be recruited so that the primary task performance remains stable (termed the performance protection response), or alternatively, performance goals can be lowered and reductions in overt performance accepted (Hockey 1997). When performance outcome is the critical feature of a situation, as is the case in most work environments, the former response is generally adopted (Hockey 1997). This response avoids primary performance reductions, however it incurs additional costs in the form of higher levels of physiological activation and subjective strain. In turn, the psychophysiological state of the worker is compromised as indicated by breakdowns in secondary task performance, adoption of simpler, but riskier strategies to accomplish performance goals, higher levels of sympathetic activation and fatigue after effects (Hockey 1997).

While work conditions may encourage the adoption of the ‘performance protection’ response, motivational factors play a decisive role in determining the amount of additional effort expended to maintain performance. The worker’s response is significantly influenced by individual differences in perceived value of task goals, response to challenges, capacity for sustained work and tolerance of adversive states associated with high levels of strain (Hockey 1997). Additionally, factors such as pre-existing fatigue and prevailing affective states influence the worker’s response (Hockey, 1997). In circumstances when work requirements exceed effort, performance breakdowns occur, either in the form of errors and accidents, or psychosomatic complaints and sick leave (de Vries-Griever & Meijman 1987; Hockey 1997).

Exposure to work environments which require workers to invest additional effort for prolonged periods of time or on a regular basis, tend to be maladaptive. In such situations, there is little opportunity for complete recovery from the fatigue generated, thereby causing a gradual depletion of the person’s available resources and leading to chronic fatigue (Hockey 1997).

A study examining the mental workload experienced by resident physicians (Bertram et al. 1992) verified the concepts described by Hockey (1997) and de Vries-Griever and Meijman (1987). Mental workload was evaluated by way of a 6 item questionnaire assessing mental effort, physical effort, difficulty, performance (2 items) and psychological stress. The results indicated mental workload was positively correlated with fatigue, thereby indicating that periods of greater mental workload placed additional demands on the physicians (Bertram et al. 1992). It was also noted that performance, as measured subjectively by the residents and objectively by external measures, tended to deteriorate during periods of high mental workload, suggesting that during these times, work requirements exceeded the resident physician’s available resources (Bertram et al. 1992).

Also partly explained by the above information is the fact that night work is more taxing than work carried out during the day (Bohle & Tilley 1989; Meijman et al. 1993; Totterdell et al. 1995). In order to overcome the natural tendency to sleep during nocturnal hours and maintain appropriate levels of arousal and performance, greater effort must be invested by the night worker. As a consequence, night workers tend to experience higher levels of fatigue than their day time counterparts (Akerstedt 1995; Luna 1997; Luna et al. 1997) and show greater decrements in performance and well-being during their first recovery day after a period of work (Meijman et al. 1993; Totterdell et al. 1995). Hence, while stressful situations may or may not manifest in visible reductions in overt performance, they are associated with a greater investment of effort on the person’s behalf which subsequently results in higher levels of fatigue. When work requirements exceed the person’s available resources, performance decrements will be observed. Chronic exposure to stressful work environments can lead to a gradual depletion of the person’s available resources and in this way, tend to be maladaptive.

7.0 FATIGUE AND PILOT PERFORMANCE

From the preceding sections of this report, it is evident that sleep loss and stress represent two of the major potential sources of fatigue in marine pilotage work. The irregular work schedules, long on-duty periods, on call nature of pilotage work and alternative sleeping environments cause reductions in sleep quantity and quality, while many aspects of the work conditions can induce stress. The combination of sleep loss and stress has an interactive and additive effect (Costa 1996), thereby potentially causing an earlier onset and more severe fatigue. As a consequence, marine pilots may be at an increased risk of exhibiting fatigue induced performance decrements. Table 1 summarises some of the recognised fatigue-induced performance decrements and how these decrements may affect piloting performance.

Table 1 Fatigue-Induced Performance Decrements and Pilotage examples

(adapted from Couper 1996; Dinges 1992a; Dinges & Kribbs 1991; Rosekind et al. 1996; Sanquist et al. 1996)

That pilotage performance can be affected by fatigue in so many different ways, all of which could potentially jeopardise safety, is disconcerting. Marine pilots play a critical role in the safe navigation of vessel and crew through difficult waters and hence, it is essential that high levels of performance are maintained by pilots at all times while on duty. However, given the disruptive effects of pilotage work schedules on circadian rhythms, sleep, social and domestic issues and stress levels, there is a high probability that at various times during work periods pilots may suffer from fatigue. Under normal circumstances this may not amount to significant deviations in performance. However, in situations when demands increase (for example during poor weather or if the pilot’s preceding work schedule has involved substantial amounts of night duty), the build up of fatigue may be sufficient to cause a breakdown in performance leading to an unwanted incident.

8.0 FATIGUE AND ACCIDENTS

The potential role of fatigue in accidents has been highlighted by a number of recent major transportation and industrial incidents. The following section of this report details the progress which has been made in substantiating the relationship between fatigue and accidents.

8.1 Prevalence of Fatigue-Related Accidents

While in the past, fatigue was often suspected of causing or contributing to many transportation accidents, the means to establish its presence was not available (TSB 1997). This was largely due to the fact that human fatigue generally leaves no tell tale signs and can only be inferred from circumstantial evidence (Brown 1994; Lauber & Kayten 1988; TSB 1997). Additionally, the lack of a universally accepted definition and standardised investigation procedures constrained researchers (McCallum et al. 1996; TSB 1997). As a consequence, the incidence of fatigue as a causal or contributing factor to past accidents has more than likely been under-reported (Lauber & Kayten 1988; McCallum et al. 1996; NTSB 1995).

Recent work however, has made some headway in increasing knowledge about the prevalence of fatigue and the role it may play in accidents. For example, the US Coast Guard Research and Development Centre identified that 16 percent of critical vessel casualties and 33 percent of personnel injury casualties occurring in US coastal waters between 1 July and 31 December 1995, had some fatigue contribution (McCallum et al. 1996). These figures were more than 10 times greater than the estimates established from data collected in 1993 (1.2 percent and 1.3 percent for vessel casualties and personnel injuries respectively) (McCallum et al. 1996). It has also been noted by the Japan Maritime Research Institute (1993) that ‘lack of alertness’ and ‘dozing during navigation’ accounted for approximately 53 percent of groundings and strandings and 38 percent of collisions occurring between 1985 and 1991. Additionally, while official statistics indicate 9.2 percent of shipping casualties occurring in Australian waters between January 1994 and January 1998 were fatigue-related, some authors have suggested that a figure closer to 30 percent would be more realistic when performance impairments due to chronic fatigue are considered (Filor 1988). These, and other findings (Sanquist et al. 1996) seem to indicate that fatigue is a widespread problem in the maritime industry and that a significant number of marine accidents are fatigue-related.

Research into other transport industries has revealed similar results. For example, it has been suggested that at least 25 percent of single vehicle road accidents (Brown 1994) and between 30 and 40 percent of heavy truck accidents (Hopkins 1992; NTSB 1995) are fatigue-related. Additionally, approximately 21 percent of all reported US aviation incidents (Reinhart 1995) are thought to have a fatigue contribution. Hence, the extent of fatigue and the role it plays in accidents appears to be somewhat greater than what past data has indicated, at least in transportation industries.

8.2 Indicators of Fatigue

To gain a greater understanding about the potential relationship between fatigue and accidents, there is a need to identify the causes and effects of fatigue, and to develop standardised procedures for investigating, analysing and reporting the role of fatigue in accidents. Accordingly, recent and ongoing work has focused on a number of these issues, with some positive results having been achieved. For instance, the US Coast Guard Research and Development Centre have identified a number of work conditions which significantly contribute to fatigue-related incidents. Those conditions identified include the number of consecutive days work prior to the incident, the number of days worked in the 30 days prior to the incident, hours on duty prior to the incident, hours worked in the past 24, 48 and 72 hours prior to the incident, changes from the normal working schedule on the day of the incident and the absence of company or union policies governing work hours (McCallum et al. 1996). While these findings were based on preliminary data, they provide a good starting point for further work.

Similarly, the National Transportation Safety Board identified that the three most important measures in predicting fatigue-related heavy truck accidents were the duration of the last sleep period, the total number of hours slept during the 24 hours prior to the accident and whether or not a split sleep schedule had been adopted (NTSB 1995). These two studies have shed some light on what appears to be an intimate relationship between the work and sleep habits of an individual and the occurrence of fatigue-related incidents.

8.3 Work, Sleep, Fatigue and Accidents

Investigations which have looked at the timing of accidents across the 24 hour cycle have revealed some interesting findings with regards to an individual’s sleep and work habits and accidents. For example, the relative risk of road traffic accidents is greatest during the early morning hours, particularly at 0300 hours, with an additional but smaller peak in accident risk occurring during the mid afternoon period (Figure 5) (Brown 1994; Folkard 1997; Hopkins 1992; Mitler et al. 1988; Summala & Mikkola 1994). This characteristic pattern in accident risk, which has also been reported for other transportation and industrial accidents, has been attributed to underlying circadian rhythms (Brown 1994; Couper 1996; Folkard 1997; Mitler et al. 1988; Sanquist et al. 1996; Summala & Mikkola 1994), and suggests that working during the circadian troughs in alertness is associated with an increased risk of accident.

Figure 5 The mean trend (and standard errors) in road traffic accident risk over the 24 hour day (after Folkard 1997)

Time on task appears to be another factor influencing accident risk. Figure 6 displays the relative risk of accidents over the course of various shift durations. With the exception of a transient peak in accident risk between the second and fourth hours on duty, accident risk increases in more-or-less an exponential manner over time, such that shifts in excess of 12 hours are associated with substantially greater risk (Folkard 1997; SIRC 1996). This finding seems to indicate that the stress and fatigue associated with long on duty periods causes an increased risk of accident (SIRC 1996). The 2-4 hour peak in accident risk evident in the figure is, at present, unable to be conclusively explained. However, one possible explanation which has been suggested is that it may reflect the need to ‘re-automise’ even highly learned skills during the first few hours of work (Folkard 1997).

Figure 6 Relative risk of accident for various work shift duration (after Folkard 1997)

Taken collectively, the results of these studies highlight the apparent relationship between sleep, work, fatigue and accidents. Work and/or sleep conditions which induce fatigue seem to be associated with a higher relative risk of accident. While this sequence of events seems logical, without standardised investigation procedures it is difficult to substantiate the relationship. Hence, the development of a fatigue index by the US Coast Guard Research and Development Centre (McCallum et al. 1996) is a positive prospect. Based upon the number of fatigue symptoms reported by the mariner, the number of hours worked in the 24 hours prior to the incident and the number of hours slept in the 24 hours prior to the incident, the fatigue index provides an objective technique for identifying those marine incidents which are likely to have a fatigue contribution. While further work is required before the fatigue index could be considered valid and reliable, the present results indicate that it should become an effective and efficient tool for establishing the likely presence of fatigue in marine incidents (McCallum et al. 1996).

8.4 Summary

It is therefore apparent that fatigue contributes to significantly more accidents than previous data indicated, and that an individual’s sleep and work patterns are two important factors influencing the risk of fatigue-related accidents. That the sleep and work conditions experienced by marine pilots are associated with a number of factors which can potentially induce fatigue is concerning. The economic, environmental and personal costs which can potentially arise from marine accidents is immeasurable, and hence, it is vital that every possible means of minimising accident risk is considered. Accordingly, underlying factors contributing to accidents need to be identified so that preventative strategies can be implemented. In line with this, ‘near miss’ reporting systems could be beneficial as such information may help to detect risk factors prior to the occurrence of a major accident (States/BC OSTF 1997).

Additionally, the adequacy of work-rest regulations should be reviewed. While the unique features of each pilotage region make it difficult, if not impossible, to impose a rigid set of work-rest regulations applicable to all groups of marine pilots, it has been recommended that individual pilotage authorities should develop work-rest regulations specifying maximum work and/or minimum rest standards (States/BC OSTF 1997). These regulations should enable pilots to begin and finish each work assignment in an appropriately aroused state and prevent the accumulation of fatigue. Consideration should be given to the type of conditions typical of the pilotage region, the duration of work assignments (including transit times), the physical and mental demands of the work, and the timing of work and rest in relation to the 24 hour cycle (States/BC OSTF 1997).

9.0 CONCLUSION

The immense responsibility associated with navigating vessels, cargo and crew through difficult waters demands that marine pilots maintain high levels of work performance at all times while on duty. However, as documented throughout this report, the work conditions experienced by marine pilots are not always conducive to optimising work performance. For example, the irregular timing of pilotage work, both in terms of its placement within the 24 hour cycle and duration of work and rest periods, may lead to disrupted sleep, circadian dissociation and a multitude of social and domestic problems. The sleeping and billeting facilities available to pilots when staying in alternative accommodation on ship and ashore, often fail to promote good recuperation between work periods and work assignments. Recent shipping reforms and commercial changes have resulted in greater workloads and increased stress for all shipboard personnel. These, and other aspects of marine pilotage work, have the potential to induce fatigue. As a consequence, breakdowns in work performance may become evident, especially in situations of increased work demands, and there may be a heightened risk of fatigue-related incident.

Given that the avoidance of unwanted shipping incidents is the primary goal of marine pilotage work, there is a need to determine the extent and nature of fatigue amongst this occupational group. Specifically, future research may examine the level of fatigue induced from (i) the irregularity of marine pilotage work, (ii) displaced and disrupted sleep; and (iii) other industry specific stressors such as on board and environmental conditions. It would also be useful to document the ways in which fatigue affects piloting performance and the potential safety consequences of this.

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