European Organisation for the Safety of Air Navigation Eurocontrol Experimental Centre

This report discusses the role of monotony in Air Traffic Control (ATC). Despite its obvious relevance as a critical individual state in air traffic controllers, monotony has not been well researched in the past. To describe evoking and contributing factors, distinguish similar critical states such as fatigue and satiation, and define countermeasures, three experimental studies were conducted with a total of 32 air traffic controllers (ATCO) in the simulated and ten ATCOs in an operational air traffic control environment. Traffic repetitiveness and (dynamic) traffic density were confirmed to evoke a state of monotony, which is indicated in reduced physiological activation, subjective sleepiness, and behavioral impairments. At the same time, reduced workload but also impaired cognitive functions were observed while fatigue increased with higher time-on-task. Higher initial recovery, the experience of flow, (dynamic) traffic density changing from low to high and active physical exercises in rest breaks were determined to have a monotony-reducing effect. Based on these outcomes, recommendations address the assessment procedures during ATC concept development as well as options for the improvement of the operational environment. The applied psychophysiological multilevel-assessment method shows otherwise undetected but critical dissociations as related to the experience of cognitive functions and motivational aspects and suggests the application of assessment procedures beyond workload ratings. In the operational environment, systematic position assignment based on predicted traffic changes, the collection of initial state information, balanced active rest breaks, trainings on the role of mental sets, and the consideration of an ATCOs psychophysiological condition in incident reporting systems are proposed. A model integrating the mentioned factors supports a systematic analysis of this issue. Future research may address the role of further individual factors related to personnel selection and the long-term development of critical states. Monotony in ATC Contributing Factors and Mitigation Strategies EUROCONTROL Project SAS-2-HF-AAAA – EEC Note No. 15/06 v FOREWORD There are various problems associated with monotony in air traffic management. The first and most obvious problem is that monotony will continue to pose a challenge to the work of air traffic controllers and thus a threat to aviation safety. One could argue that increases in air traffic demand and the associated increase in controller workload will render this problem obsolete yet, unfortunately, this is not the case. Monotony due to very low traffic load will continue to play a role for example in night shifts, resulting in problems of vigilance. More importantly perhaps, monotony related to repetitive traffic patterns may play an increasing role since the need to manage higher traffic loads in busy periods might lead to increasingly uniform traffic patterns. Future levels of automation could further aggravate this problem. The second and perhaps less obvious problem is that to date we have a limited understanding of what monotony actually is, particularly in the area of air traffic management. The construct itself is not very well defined: the term monotony is sometimes used as referring to an operator’s state and sometimes to denote a situation inducing such a state. The factors contributing to an operator state of monotony are not very well understood either. And finally the consequences of monotony in terms of air traffic controllers’ performance are not fully understood. A further problem might become more apparent as soon as the factors contributing to monotony and the impact of monotony on operator performance and well-being will be better researched, namely the prevention and mitigation of monotony. The first solution that comes to mind would be to avoid work situations proven to increase monotony and impair performance. However, in some instances that may be either impractical or simply impossible. Whilst there is a sense that mitigation may help in such cases we have a very poor understanding of how we can mitigate monotony. For the above reasons EUROCONTROL has decided to sponsor research in the field of monotony through a Ph.D. scholarship for Sonja Straussberger. I had the privilege and pleasure to supervise Sonja’s Ph.D. thesis at EUROCONTROL. I am very pleased with the results of her research and I am convinced they will make a significant contribution to ATM research. Dirk Schaefer EEC Quality Manager EUROCONTROL Monotony in ATC Contributing Factors and Mitigation Strategies vi Project SAS-2-HF-AAAA EEC Note No. 15/06 Page intentionally left blank Monotony in ATC Contributing Factors and Mitigation Strategies EUROCONTROL Project SAS-2-HF-AAAA – EEC Note No. 15/06 vii ACKNOWLEDGEMENTS In a marvelous description of the history of experimental psychology in an edition published in 1956, Edward Boring determined two limitations for scientific advance. The first one is ignorance, which means that discovery depends on another discovery being made to open its way. The second one is when discovery is limited by the habits of thought that pertain to the culture of any region or period. Boring called this phenomenon Zeitgeist. With this statement in mind, I am in the pleasant situation to acknowledge the aid and cooperation of numerous persons who enabled research on a subject which was trying to overcome these limitations. First of all, I am indebted to my supervisors, Professor K. Wolfgang Kallus, Department of Work-, Organizational and Environmental Psychology at the Karl-Franzens-University Graz, for the academic supervision, and Dr. Dirk Schaefer, EUROCONTROL Experimental Centre, Brétigny sur Orge, for the industrial supervision. I was fortunate to have the inspiring guidance and encouragement of two exceptional thinkers, who made it possible to arrange this research thanks to their unbureaucratic, flexible, and open attitudes. Furthermore I owe a very special vote of thanks to Professor Dr. Peter Jorna and Mr. Alistair Jackson for taking their time for encouraging statements, the reading and assessing processes and the discussion. Their creative minds gave me valuable insights in relevant relationships. My expression of thanks is long over-due to numerous air traffic controllers and experts who patiently and curiously participated in the data collection, the study preparation or the completion process. This also includes the persons who enabled access to control centers or volunteered in the local organization of the studies. Also, without the kind support of many colleagues at EUROCONTROL the current work would not have been possible. This research was funded by EUROCONTROL Experimental Centre and enabled by the progressive engagement of proactive people who made this work possible. Hopefully, many students will be able to make use of such an opportunity in future. Finally, special thanks are due to those who supported me personally. My partner Laurent for his never-ending understanding, my family for supporting my career, and my friends for who distance does not matter and who have been there to help out any time. The opportunity to conduct the studies autonomously and learn greatly contributed to develop a better understanding of science in an applied field and to take the responsibility work psychologists have representing the human component in a technical field. More than anything, the work reinforced my understanding of the significance of scientific ethics in applied environments. This approach was also significantly influenced by the critical discussion of Schmidtke in 2002 of research trends in the field of ergonomics and the present disinformation in publications. He emphasized the responsibility of the researcher to carefully apply scientific methods for the scope of increasing knowledge that can be applied to solve practical problems. Certainly, a lot of people are involved in the completion of such a big work. As it is not possible to mention all of them by name on one page, everyone else who is concerned definitely will know that these special thanks are TO YOU. EUROCONTROL Monotony in ATC Contributing Factors and Mitigation Strategies viii Project SAS-2-HF-AAAA EEC Note No. 15/06 Page intentionally left blank Monotony in ATC Contributing Factors and Mitigation Strategies EUROCONTROL Project SAS-2-HF-AAAA – EEC Note No. 15/06 ix SUMMARY Despite the obvious relevance of monotony in the field of air traffic control (ATC), it has not been well researched in the past. One of the reasons is related to the unclear use of monotony to designate the task characteristics as well as the individual reactions to these characteristics. At the same time, the more frequently addressed concepts of boredom, underload, and low vigilance were not clearly distinguished and kept apart from critical states such as fatigue and satiation. While these states are similar in appearance, the occurrence of either state requires different countermeasures. Moreover, existing research results cannot be directly applied to understand monotony in ATC, as they were obtained in different industries or focused on isolated components. In addition, previously developed models to explain the effects of task execution on performance and individual states are often restricted on few components and thus do not well represent the conditions contributing to monotony. For the current work, a framework was used that clearly distinguished between the description of task characteristics in terms of uneventfulness and repetitiveness and exclusively used monotony for the description of an individual state. Based on research results obtained by Bartenwerfer (1957), monotony was characterized by physiological deactivation, increased feelings of tiredness and boredom, and fluctuating performance. Under consideration of individual and organizational factors, the framework allowed not only investigating the effect of task characteristics, but also the distinction of critical states through the assessment of multiple indicators on a physiological, subjective, and behavioral level. To determine task and individual factors that evoke, enhance or mitigate monotony in ATC, to distinguish critical states and to define countermeasures, three studies were conducted. In simulated air traffic control settings a small-scale experiment with eight operational experts (not active controllers) and a main study with 24 air traffic controllers were run. Ten air traffic controllers participated in a field study executed in an European Control Center. As repetitiveness is an important component not only in the current air traffic management (ATM), but also in future concepts favoring air traffic synchronization, it was centered in the research activities. In addition, it was assumed that repetitiveness might have a different impact depending on the level of dynamic traffic density. The main simulation experiment was based on the small-scale study and involved a 2 (break activity) x 2 (repetitiveness) x 2 (sequence of dynamic density) x 2 (run) x 3vs.15 (interval) -mixed design with repeated measures on the last two factors. Two traffic scenarios of 45 minutes each were executed and a short third scenario was introduced to determine the effects of break activity. The dependent variables comprised heart rate (HR) and its variability (HRV), skin conductance level, blink rate, and the power in common frequency bands of spontaneous brain activity. On a subjective level, scales assessed mood, workload, and the perceived cognitive, emotional and motivational state during and after the scenarios. Behavioral and performance measures assessed the occurrence of Short Term Conflict Alerts (STCA). HR, sleepiness, and the subjective feeling of monotony were integrated in a standardized indicator for the state of monotony based on the small-scale study. Higher monotony occurred if participants were exposed to repetitive scenarios. The effect of monotony was reinforced in the low density condition of the first run and also reflected in tendencially increased conflict resolution time in an unexpected situation. The comparison of indicators for the critical states revealed that monotony as a consequence of task repetitiveness was clearly found in the first scenario, but overlaid by time-on-task effects resulting in higher fatigue with the ongoing second scenario. The distinction of critical states did not allow a clear statement concerning satiation. While the sequence of dynamic density changing from high to low from the first to the second run still increased the cognitive impairments, a motivating and monotony-decreasing effect of the dynamic density changing from low to high was found. EUROCONTROL Monotony in ATC Contributing Factors and Mitigation Strategies x Project SAS-2-HF-AAAA EEC Note No. 15/06 The monotony-decreasing effect of active exercises in rest breaks was confirmed, even though there was no favoring effect after repetitive conditions. Boredom proneness and initial recovery and strain states were not confirmed to be a significant factor contributing to monotony; marginally significant effects do however indicate the relevance of further investigation. On the other hand, if individuals perceived flow during task execution in the first run, the indicator for the state of monotony was lower. In the operational environment, a 2 x 2 within-subject design was deployed with high versus low repetitiveness and high versus low traffic load in sectors. Controllers participated in 90-minute-work periods that had been selected based on supervisors’ ratings and traffic statistics. Physiological indicators comprised HR and HRV, the previously used subjective scales and questionnaires were extended with ratings for traffic characteristics, and performance indicators were collected through subjective ratings of related behaviors. The effects of repetitiveness on the composed indicator for the state of monotony were confirmed. A more detailed analysis revealed that – in contrary to the simulated environment the effects were not reflected in the summarized physiological measures during a work period. Controllers experienced reduced motivation, attentiveness, concentration, and increased boredom, but also reduced workload and strain. Some of these effects were even more pronounced in the low traffic load condition. Apart from that, subjectively perceived motivation and the combined indicator for the state of monotony were higher if a change of traffic density from low to high was perceived during a work period. Nonetheless, the description of individual cases showed covered physiological effects which turned out to be rather the consequence of clearly distinguishable events on the individual level. Delayed and immediate effects on blood pressure were observed under consideration of personally relevant occurrences. On an individual level the initial state of recovery at the beginning of the work day was confirmed to influence the development of critical states. At the same time the collection of organizational processes helped to understand changes in subjectively perceived satiation. The total of the results supports the assumption that repetitiveness in task conditions is evoking monotony in both simulation and field settings, which is mitigated by the state of recovery at the beginning of the work shift. The potential influence of boredom proneness and the unexpected effect of flow experience require further investigation. The contradictive results in the physiological indicators are explained by behaviors executed by air traffic controllers to remain active. The results do not support any interpretation related to stress, as opposed to research studies that used ATC-related tasks workload was also reduced. This led to propose a model of monotony that considers the task factors repetitiveness and uneventfulness, the individual boredom proneness and states at the beginning of the work shift as well as organizational factors to assess monotony with the help of physiological, subjective, and behavioral indicators. The distinction of other states such as fatigue and satiation and a positive state of flow is essential, even though with the current data the definition of satiation remains unclear. Based on these outcomes, recommendations address the level of ATC concept development as well as the improvement of the operational environment. Several methodological issues are stressed to be considered in simulation set-ups. They contain the multi-level approach to assess controller states as a task consequence, the selection of increased scenario duration, and sufficient training in new concepts. Especially a one-sided assessment of workload ignores further negative effects as related to cognitive functioning and motivational aspects. In the operational environment, the systematic consideration of changes in traffic density and collection of initial state information call for a systematic assignment of controllers to work positions based on traffic predictions to make use of their motivating and monotony counteracting potential. Trainings may include further sensitization towards the effect of habits and mental sets and also provide better strategies for balanced rest breaks and systematic communication. Finally, the collected statistics in incident reporting systems should be extended by better categorized information on the controller’s psychophysiological states. Overall, future questions may address the role of further individual factors related to personnel selection and the long-term development of critical states. Hence, monotony remains a challenging issue within the ATC environment. Monotony in ATC Contributing Factors and Mitigation Strategies EUROCONTROL Project SAS-2-HF-AAAA – EEC Note No. 15/06 xi TABLE OF CONTENTS LIST OF APPENDICES................................................................................................... XIII LIST OF FIGURES .......................................................................................................... XIV LIST OF TABLES............................................................................................................ XVI ABBREVIATIONS AND ACRONYMS.............................................................................. XX REFERENCES ............................................................................................................... XXI