Background and Significance of the Topic
Air transportation is in high demand among people worldwide due to its speed and efficiency. According to Jiménez-Martín et al. (2020), “air transport is growing exponentially, from 3.8 billion air travelers in 2016 to 7.2 billion passengers expected to travel in 2035” (p. 1). With this increase predicted, companies in the aviation industry are expected to start experiencing labor shortages, which is already a serious issue (Jiménez-Martín et al., 2020).
One job position that has always been affected by shortages is that of an air traffic controller (ATC). ATCs’ roles involve directing aircraft to separate them to avoid collisions. Their work involves providing pilots with the necessary information as they fly in the air or taxi on the ground, ensuring that air traffic is unimpeded and enhancing the safety of air travel (Kouba et al., 2023). As a result, air traffic control must be available 24 hours a day in most airline companies, leading to controllers working shifts that, in turn, cause fatigue in these professionals.
Importance of Fatigue Management in Air Traffic Controllers
Air traffic control facilitates the flow of airspace and airport surface traffic, thereby avoiding potential collisions between aircraft. For professionals in this area to satisfy this critical safety constraint, they must always be in the right state to detect and solve possible conflicts between trajectories (Kouba et al., 2023). However, Shen et al. (2020) note that, despite the significant growth in the number of flights in recent years, the growth of ATCs has been relatively low. As a result, the available ATCs must keep up with the increased workload pressure, which has been associated with fatigue (Jiménez-Martín et al., 2020).
This situation has led to numerous air traffic accidents at the airport, often resulting in collisions between planes. For instance, a report by Nunes & Cabon (n.d.) notes that in 2010, ATCs’ fatigue caused an Indian jet to plunge on a cliff while attempting to land, leading to 158 deaths. Therefore, managing fatigue will contribute to the operational efficiency of air traffic control and prevent accidents that might lead to deaths and damage. Additionally, fatigue management is crucial for ensuring that ATCs maintain better health and perform effectively.
Purpose and Scope of the Literature Review
Fatigue is a serious issue among ATCs and puts passengers’ safety in jeopardy. Therefore, this literature review aims to analyze the validity of measurement tools used in air traffic control for assessing fatigue and determine their suitability for shift work assignments. This review will provide an in-depth examination of various measurement tools used to assess fatigue among ATCs, including performance-based measurement tools, subjective measurement tools, self-report measures, fatigue questionnaires, and physical indicators (Shen et al., 2020).
By evaluating the validity of these tools, this paper aims to enhance the public’s understanding of the strengths and weaknesses of each approach. The tools included are the most appropriate and reliable ones in effectively assessing fatigue among these individuals, mainly due to the nature of their work. The scope of this literature review includes relevant scholarly journal articles, empirical studies, reports, and other credible sources as of 2019.
Theoretical Framework and Conceptual Understanding of Fatigue
Definition and Conceptualization
A person’s capacity to maintain intense or sustained cognitive and motor tasks is essential in their daily lives and is required in their vocational, physical, and educational activities. According to Behrens et al. (2023), fatigue is an umbrella term used to refer to the psychological processes that inevitably accompany people during their motor and cognitive activities that exceed a particular duration or intensity. Over the years, various theoretical perspectives have provided more profound insights into the nature and manifestation of fatigue.
For instance, the energy conservation theory is a perfect example of a model that explains fatigue. This theory claims that fatigue occurs when a person’s energy is depleted (Azizi et al., 2019). Therefore, fatigue occurs when a person has worked longer than their body can manage.
Factors Influencing Fatigue in the Shift Work Environment
Shift work settings, including those for air traffic controllers, present specific challenges that affect fatigue. According to Mahdavi et al. (2020), poorly designed shift-working arrangements and working hours, such as irregular work schedules, disrupted sleep patterns, and frequent shifts between night and day work, can affect a person’s sleep and wakefulness. These disruptions then lead to poor quality or insufficient sleep, which influences fatigue.
Other factors that have been linked to the development of fatigue in shift work environments include environmental and social conditions, such as reduced social support, increased noise in the workplace, and disruptions to personal life (Mahdavi et al., 2020). Most of these factors are available in shift work environments.
Effects of Fatigue on Air Controller Performance and Safety
Fatigue has adverse effects on the performance and safety of ARCs. For instance, Zhang et al. (2019) conducted a study on 19 participants to examine the effects of fatigue and stress on air traffic control performance. The findings suggested, “fatigue mainly makes controllers’ execution speed slower and less consideration about the situation” (Zhang et al., 2019, p. 1). It affects ATCs’ performance and impairs their attentiveness and sharpness, leading to dangerous areas in airports, which impacts safety.
Performance-Based Measurement Tools
Overview
Fatigue affects the performance efficiency of ATCs, leading to dangerous incidents in airports. Therefore, to assess whether an ATC is fatigued, a performance-based measurement tool can be a practical approach. Performance-based measurement tools are among the most effective methods used over the years to assess fatigue among ATCs by evaluating their psychomotor and cognitive performance (Zhang et al., 2021).
One of the most commonly used performance-based measurement tools is cognitive tests (Zhang et al., 2021). The cognitive tests evaluate a person’s mental functioning that is impaired by fatigue, including decision-making, memory, attention, and speed of information processing. For instance, the psychomotor vigilance task (PVT) measures sustained attention and reaction time(Zhang et al., 2021). It is an objective measure of cognitive functioning used to investigate fatigue.
Validity and Assessment
Performance-based measurement tools for fatigue satisfy many criteria that make it variable. When measuring the variability of a fatigue measurement tool, many considerations are taken into account. According to Frimanson et al. (2021), some of the essential aspects that cognitive tests and other performance-based measurement tools must meet include sensitivity to performance and the ability to predict real-world outcomes.
Cognitive tests, such as the PVT, measure how a person has been affected and can no longer attend to their roles (Zhang et al., 2021). For instance, it measures how an ATC’s performance declines as the level of fatigue rises. As a result, it indicates that the individual cannot continue to be efficient in their work and needs to rest.
In essence, the tool predicts that fatigue in the ATC puts the airport’s safety in jeopardy. In a shift work environment, such as that of ATC, individuals must have sustained attention, make decisions quickly, and process information accurately (Jiménez-Martín et al., 2020). Therefore, with these performance-based tools, one would easily identify if an ATC is capable of being efficient in its work.
Subjective Measurement Tools
Overview
Subjective measurement tools have also been widely used in different settings to help assess fatigue among workers. According to Vergauwen et al. (2021), subjective approaches often rely heavily on individuals reporting their own fatigue when they recognize it. Self-reporting involves people rating their experiences subjectively on a descriptive or numerical scale (Díaz-García et al., 2022). In many instances, these scales may include questions seeking to investigate an individual’s mental fatigue, general fatigue, overall energy levels, or physical fatigue.
Over the years, many subjective measurement tools have been developed to help ensure workers are effective in their roles. One of the most common subjective tools is the visual analog scale (VAS) (Díaz-García et al., 2022). Díaz-García et al. (2022) note, “for mental fatigue, the subjectively reported Visual Analogue Scale (VAS) has been the most used instrument” (p. 3). While using this tool, people are required to mark their responses along a continuous scale or line that would help indicate their level of fatigue.
Validity and Assessment
The visual analog scale (VAS) has proven valid in measuring and assessing fatigue in many aspects. First, VAS has construct validity for measuring fatigue, as noted by Díaz-García et al. (2022), and likely other types as well. According to Vold et al. (2021), the VAS has demonstrated validity in measuring fatigue in patients recovering from severe medical conditions, such as stroke. Díaz-García et al. (2022) report that in many studies, a higher VAS score correlates with self-reported levels of sleepiness, tiredness, and low energy levels.
Another aspect that makes this fatigue measurement tool valid for ATCs is its sensitivity to change in an individual. For instance, Vold et al. (2021) note that VAS can be used to detect changes in a person’s fatigue level after shift work, lack of sleep, and prolonged working periods. Therefore, VAS is an effective tool for measuring ATCs’ fatigue because it provides accurate findings and can detect changes that may impact their overall performance, ensuring safety in airports and facilitating effective traffic management.
Psychological Measures of Fatigue
Overview
Apart from performance-based and subjective measurement tools, psychological measures have also proven effective in assessing an individual’s level of fatigue. Unlike subjective tools that rely on a person’s ratings, psychological measures of fatigue are objective, with their findings based on mental parameters (Bjegojevic et al., 2021). An example of a commonly used psychological measure is electroencephalography (EEG).
EEG is a standard test that medical specialists often use to detect abnormalities or electrical activity in people’s brain waves (Bjegojevic et al., 2021). It is a psychological approach to detecting fatigue in individuals by assessing brain state and muscle activity, similar to those that measure eye movement and heart rate variability (Ren et al., 2021). This psychological measure has been used in many instances in assessing fatigue because it offers insights into its neural correlates. This method captures an individual’s brain patterns that occur during their cognitive processes, state of consciousness, and alertness levels (Ren et al., 2021). This ability makes it an effective measurement tool for identifying the level of fatigue in ATCs.
Validity and Assessment
Psychological measures, such as EEG, have proven to be an effective measurement method for assessing ATC’s level of fatigue. One of the aspects that makes EEG a valid tool for assessing fatigue in shift work among ATCs is its sensitivity in detecting slight changes in an individual’s state. EEG’s ability to detect patterns in the brain makes it able to notice if a person has a change in their fatigue level (Ren et al., 2021). For instance, if an ATC has not had sleep for a long time and has been working continuously, the EEG will notice that their fatigue level has significantly increased, helping to avoid accidents in the airport.
This tool can be used in both field and laboratory settings, making it also suitable for the work at hand. In both settings, activities may include identifying the factors that have induced fatigue, such as a higher number of aircraft departing or landing at an airport and other traffic control scenarios (Ren et al., 2021). However, this approach presents a challenge, as it requires specialized equipment, data analysis expertise, and precise electrode placement (Bjegojevic et al., 2021). This deters many air transport organizations from adopting it to help measure fatigue among their ATCs.
Fatigue Questionnaires and Self-Report Measures
Overview
Fatigue questionnaires and self-report instruments are methods for evaluating an individual’s fatigue levels in shift work settings, using a subjective approach. According to Vergauwen et al. (2021), these measurement tools often consist of many questions whose intentions are to capture different fatigue dimensions, such as effect, frequency, severity, and the symptoms exhibited. One notable example of fatigue questionnaires and self-report measures is the Multidimensional Fatigue Inventory (MFI).
MFI is a 20-item self-report instrument comprising five subscales: mental fatigue, reduced motivation, reduced activity, physical fatigue, and general fatigue (Westenberger et al., 2022). These subscales measure different kinds of fatigue, including a person’s overall, mental, and physical exhaustion, weakness, and lack of energy. Each subscale has a Likert scale that ranges from 1 to 5, with five representing “yes” and one indicating “no.” Over the years, this approach has been employed in numerous research settings and assessments aimed at identifying and addressing fatigue among workers (Westenberger et al., 2022; Vergauwen et al., 2021). It can help assess the fatigue levels of ATCs and ensure safety in airports.
Validity and Assessment
Fatigue questionnaires and self-report measures, such as MFI, have proven effective in assessing people’s fatigue levels. In a study by Westenberger et al. (2022) investigating the psychometric properties of the MFI among a sample of the German population, the findings suggested that the MFI is a reliable and valid tool for measuring fatigue. For instance, MFI’s content validity is based on its multidimensional nature, including general, physical, and mental fatigue, as well as reduced motivation and activity support (Westenberger et al., 2022).
Additionally, Westenberger et al. (2022) note that the subscales in MFI correlate with constructs related to fatigue and measures, such as quality of life and depression. This indicates that MFI, like other fatigue questionnaires and self-report measures, supports its construct validity. MFI also meets the convergent validity of the tools used in assessing fatigue. According to Westenberger et al. (2022), “all correlations between the MFI-20 subscales/total score and the SF-36 domains/PCS/MCS were significant (p < 0.001), using Spearman’s ρ correlations due to the non-parametric distribution” (p. 5). Therefore, fatigue questionnaires and self-report measures would be significant tools in investigating fatigue among ATCs.
Challenges and Future Research
Challenges in Assessing Fatigue in Air Traffic Controllers
In different nations, the rising number of people traveling by aircraft has increased the workload in airports, which has resulted in fatigue among workers, including ATCs. Since fatigued ATCs have caused serious aircraft accidents in airports in recent years, many strategies have been developed to assess their states during work. However, according to Shen et al. (2020), “the conventional fatigue-detecting methods based on speech are neither effective nor accurate” (p. 1). These challenges arise from the nature of the work and the context of ATCs.
One key issue encountered when assessing fatigue among ATCs is the subjective nature of fatigue, which hinders the effectiveness of objective tools, such as cognitive tests and EEG (Ren et al., 2021). Shen et al. (2020) add that some measurement tools are ineffective since “speech signals are nonlinear and complicated” (p. 1). Others include individual variability, operational demands, and dynamic work schedules of ATC.
Emerging Technologies and Advancements in Managing Fatigue
Since the beginning of the 21st century, the world has undergone significant technological development, transforming various sectors of society. In the healthcare sector, Junaid et al. (2022) note that technology has helped advance the delivery of care and make it more personalized. Such technological advancement can also be employed in managing fatigue in the near future.
An example is smart devices, such as wearable sensors, which have the capacity to store and transmit essential patient data and information (Junaid et al., 2022). When it comes to managing fatigue among ATCs in airports, wearables can be used as a tool for observing and tracking their status, including sleep patterns, activity levels, and physiological signals (Behrens et al., 2023). The sensor will provide real-time feedback and help identify fatigue before it leads to a collision between aircraft.
Other emerging innovations that can help manage fatigue include data analytics, machine learning (ML), artificial intelligence, the Internet of Things (IoT), and Blockchain technologies (Junaid et al., 2022). All these emerging technologies promise solutions to effectively detecting fatigue among ATCs in the air transportation sector.
Areas of Future Research and Improvement in Assessing the Validity of Measurement Tools
The literature review above has indicated that fatigue is a serious issue among workers in shift work environments, such as ATCs. Additionally, it has become a challenge to determine the validity of most measurement tools in identifying fatigue during the early stages and in helping to manage it. Therefore, there is a need to conduct future research on how to enhance the validity of fatigue measurement tools. This can be achieved by conducting longitudinal studies that track fatigue by simulating realistic air traffic control scenarios, as well as referring to various scholarly articles (Kouba et al., 2023). Addressing these areas would help enhance the assessment of fatigue investigation approaches.
Conclusion
This literature review has explored the validity and assessment of fatigue measurement tools for ATCs in shift work environments. The air transport industry has significantly boomed in recent years, which has stretched the number of ATCs, hence leading to their fatigue as their workload has increased. Fatigue has been a significant issue in air traffic control, as it limits their overall performance and compromises safety in airports. Many measuring tools for fatigue would help detect this condition and avoid accidents. However, there are many challenges affecting the validity of these approaches, hence the need to leverage emerging technologies and future research to gain a deeper understanding of how to manage fatigue.
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