Fatigue in an Irregular Shift System in Air Traffic Control

Maximilian Peukert

AutorIn

Maximilian Peukert

Titel

Fatigue in an Irregular Shift System in Air Traffic Control

Zitierfähige Url:

https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-941896

Übersetzter Titel (DE)

Müdigkeit in einem unregelmäßigen Schichtsystem in der Flugsicherung

Erstveröffentlichung

2024

Datum der Einreichung

14.06.2024

Datum der Verteidigung

21.10.2024

Abstract (EN)

The operational work of air traffic controllers (ATCOs) is characterized by continuous and demanding cognitive tasks. Duties include ensuring a safe and efficient movement of aircraft, often operating in a 24/7 system necessitating shift-based work schedules. However, the nature of shift work introduces significant challenges related to fatigue and its potential impact on performance and safety. Fatigue is a complex physiological and psychological phenomenon originating from multiple factors such as prolonged wakefulness, inadequate sleep, and disruption to circadian rhythms. Those aspects are mainly influenced by working times, shift work, and the shift system itself. Fatigue can impair cognitive functions, including attention, reaction time, decision-making, and memory recall – critical abilities for ATCOs. Organizations and regulators are mandated to develop approaches aimed at reducing fatigue and the associated risks. Currently, fatigue is often managed through a compliance-based approach, which prescribes strict duty time limitations. However, this method oversimplifies fatigue as a non-issue in the workplace, merely because these limitations are adhered to. Recognizing the inaccuracy of this approach, a risk-based approach has been introduced. The approach acknowledges that varying degrees of fatigue risks may be present throughout a shift. This psychologically more accurate perspective has driven a change towards the fatigue risk management system (FRMS). A given shift system has a major influence on fatigue and is critical for any FRMS introduction. The actual shift design and scheduled roster can vary between industries and among air traffic control (ATC) organizations. Heterogenous shift systems differ in terms of fixed or irregular rotation, rotation direction, shift length, recovery times, minimum time between consecutive shifts, and maximum of worked hours per week or month. The impact of these factors on fatigue is, however, underexplored in ATC. A critical consideration of the shift system is indicated. For this dissertation, an irregular and preference-based shift system was investigated. Irregular shift systems, as opposed to fixed shift schedules, offer more variability in the distribution of work shifts over a roster period. The shift combinations do not follow a fixed order. Preference-based shift systems allow workers to request individualized rosters, encompassing their preferred shift types and duty days for the roster period. Particularly with regard to an irregular and preference-based shift system in ATC, there is a lack of systematically obtained fatigue data. The aim of this dissertation is to enhance the understanding of fatigue in an irregular and preference-based shift system in ATC. The shift system was investigated with a focus on fatigue dynamics and their relation to shift types, rostering factors, and night shift design as well as the consistency of subjective and objective fatigue data. In order to understand fatigue in the given irregular shift system, two field studies were conducted at different points in time, using a widely identical methodological approach. Both studies were conducted at an area control center. Fatigue was measured with a subjective and an objective method over a three-week period in all operational shifts at three key timepoints: beginning, middle, and end of the shift. Study 1 covered all four shift types (including morning, evening, and two night shifts) and investigated the differences within and between shift types. Moreover, the influence of the rotation direction and time between shifts was investigated. The results revealed a positive association between time on shift and objective fatigue. Objective fatigue increased significantly in the first half of all shifts, but then maintained at a certain level. However, this effect was moderated by the time of day, with night shifts resulting in overall increased objective fatigue in the middle and end of shifts compared to day shifts. Subjective fatigue increased over time only for the evening and one night shift type. Comparisons between shift types mostly showed higher subjective fatigue during night shifts compared to day shifts. Time on shift appeared to be the most relevant fatigue factor for day shifts, while the time of day was more relevant for night shifts. Individuals working the night shift had a longer continuous duty time, which likely explains the association with fatigue, even though task demands tend to be lower at night. Considering the rostering factors, shift combinations that had less than 11 hours between shifts (quick returns) and a counterclockwise rotation direction were associated with increased fatigue at the beginning of the subsequent duty. Interestingly, this effect diminished as the shifts proceeded. Analyses of the sleep quantity prior the shifts showed differences between all shift types, with the shortest sleep duration before morning shifts and longest prior to evening shifts. Discrepancies between subjective and objective fatigue were found. Study 2 focused on night shifts. A single split night shift arrangement was given. The arrangement included two mirrored night shift types (NA and NB), with sleep and operational phases alternating mid-shift. Both shifts commenced at 10 p.m., with NA starting operational work while NB begun with a sleep phase and being on-call. Around 3 a.m., NB took over from NA and continued operational work until the end of the shift at 7 a.m., while NA had the opportunity to sleep from 3 a.m. onwards and remaining on-call. In addition to the measurements at the key timepoints, subjective fatigue data was collected at four times during the operational work phase. The investigation of the split night shift arrangement showed that, regardless of the night shift type (NA or NB), there was a main effect of time on shift for both subjective and objective fatigue. Comparisons between both night shift types revealed minimal differences. Subjective higher fatigue was observed at the beginning of the shift for NB, although this effect was not observed for objective fatigue. Analysis of sleep duration prior to operational work revealed different preparation mechanisms among participants depending on the type of night shift worked. Specifically, the analysis showed that the average sleep duration prior to the shift was more than one hour shorter for NB compared to NA. However, the cumulative sleep duration prior to the operational work phase was longer for NB, as they achieved an average of three hours and 46 minutes of on-shift sleep. Again, discrepancies between subjective and objective fatigue were found. The objective of enhancing the understanding of fatigue in an irregular and preference-based shift system in ATC has been achieved. A positive association between time on shift and fatigue was found across both studies, predominantly in the first shift half. The results emphasize the crucial role of rostering in subjective and objective fatigue. The revealed discrepancies between self-evaluated (subjective) and performance-based (objective) fatigue might lead to safety risks, as individuals are not aware of reduced performance capabilities due to fatigue and they may request inadequate shift combinations. The interaction of fatigue with secondary factors is discussed, highlighting considerations when implementing an FRMS.

Verweis

Study 1
Link: https://drive.google.com/file/d/1zhvYcFQHlioXuo6xpqI9uWjRfUqC5EXG/view
The Influence of Rostering Factors on Fatigue in an Irregular Shift System in Air Traffic Control

Investigating Fatigue in Operational Nightshifts: A Study of Work–Sleep Organization in Air Traffic Control
Study 2
DOI: 10.1027/2192-0923/a000264

Freie Schlagwörter (EN)