Operational pressure and the SHP framework: Connecting the dots for safety

Operational pressure refers to pressure, whether induced or self-induced, that can affect the (flight) operation and may also impact safety. It is a hot topic in many sectors, being an important reason for multiple personnel strikes - the aviation sector is no exception here. Given the rapid evolution of these different operational pressures as the world adapts, continuous attention will be necessary for addressing the concept of operational pressure and discovering new mitigation strategies. Therefore, this paper delves deeper into both current and future factors influencing operational pressure, as well as mentioning some potential mitigating measures. Moreover, the case of operational pressure is structured and visualised using NLR’s Safety & Human Performance (SHP) framework. The result provides a structured overview of the impacts of different operational pressures on safety, which can aid in developing mitigations to lessen the effect of such pressures.


Introduction
The concept of "operational pressure" refers to pressure, whether induced or self-induced, that can affect the operation and may also impact safety.The topic has been increasingly in the news, as it has become one of the main reasons for the increased number of strikes; The aviation sector is no exception here, with many overworked employees working globally (Hughes, 2022).
Researching topics such as operational pressure can be a difficult task, as it is a widespread problem in a system that consists of many actors and organisations.Hence, it can be valuable to use tools to structure and guide thinking about such phenomena.This is the precise reason that the Safety and Human Performance (SHP) framework was developed.
The aim of the present paper is hence threefold.First, the aim is to define and investigate the different sources of operational pressure and its contributing factors, specifically in the aviation domain.The second aim is to introduce and explain the SHP framework.Finally, these two lines of research come together in the third aim of this paper, which is to apply operational pressure to the SHP framework.

Description of operational pressure
Operational pressure -or related topics such as psychological well-being at work and work stresshave been studied considerably, especially since the seventies.Motivational problems were becoming more prevalent in work settings, and the word "burn-out" was used for the first time during that period (Freudenberger, 1974).An organisational focus on work stress and employee well-being became an important aspect from that moment on.Whereas most research in the 20 th century focused on job motivation (Deci & Ryan, 1985;Hackman & Oldham,1976), this focus shifted a few decades later towards models and questionnaires explaining psychological well-being or work stress (Kompier, 2003;Kristensen, Hannerz, Høgh & Borg, 2005;Palmer, Cooper & Thomas, 2004).
Looking at it from a birds-eye view, all these different models suggest that work stress can either stem from the organisational environment, or from within the employee themselves.The organisational factors influencing work stress can be categorized into a) the job characteristics (e.g.job demands, workload, shift work and autonomy), b) the employee's feeling towards the job (e.g.meaningful, competence, role ambiguity), c) relatedness (e.g.social support, relationships, feedback) and d) organisational aspects (e.g.commercial pressure and staff shortage).The personal factors can be categorized into a) self-induced pressure (the urge to do well), b) a poor work-life balance and c) private situations affecting you mentally (e.g.personal health, relationship issues or financial difficulties).
These identified factors are relatively general and can hence be applied to different operational environments, including aviation.However, some of these factors are especially relevant for the aviation industry.The 24/7 operations result in irregular work schedules for most aviation personnel, dealing with passengers requires emotional demands, and some tasks -such as air traffic control -require a high cognitive workload.On top of that, as in many professions nowadays, staff shortage is an issuewhich can result in a higher workload and longer working hours.Finally, commercial pressure is a major influence on work stress in the aviation sector.To illustrate this, a study on small commercial airlines in Alaska revealed that pilots felt pressure to be productive and efficient because the company needed to be profitable, and could not lose clients.This pressure led to unsafe decisions, such as refraining from requesting weather updates because they intended to depart regardless of the conditions (Bearman, Paletz, Orasanu, & Brooks, 2009).
It is likely that in the future, these factors will only increase in number and severity.Moreover, it is expected that the coming years will be characterized by a further digital transformation, higher levels of autonomy (resulting in more human-machine teaming), and new platforms and mobility concepts that increase air traffic density (CIEHF, 2020; EREA, 2021).Finally, the climate crisis may influence safe operations to an increasing extent: extreme winds can cause operational disruptions on runways, while storms will cause flight schedule disruptions, damage to aeroplanes, and flooded runways (Eurocontrol, 2021).These consequences are additional operational pressures, and can hence contribute to even more work stress.

Interviews
Considering the explanation of operational pressure as described above, interviews with current aviation practitioners were conducted to validate and complement this phenomenon.The participants worked in different Dutch aviation organisations -ranging from airport to airline, and ground handling to air traffic control -and had a managerial or advisory function related to safety.In total, seven individual interviews were conducted, complemented by three plenary sessions with 46 participants.Each plenary session consisted of the same participants.
The interviews revealed that work stress is prevalent throughout the whole aviation sector.Some of the main factors of influence validated the theoretical conclusions.These are a) high workload (due to too much work or time pressure), b) last-minute changes in planning, c) self-induced pressure (due to feeling responsible) and d) the social safety of the working environment.It was expected that e) humanmachine teaming, f) operator monitoring, g) extreme weather due to climate change and h) congested airspace would be influencing factors on future work stress.
On top of these practical validations of the theoretical literature, additional factors were identified that influence work stress.These are i) commercial pressure, j) ambiguity of rules and regulations, Man-Machine Interaction or new technologies in general, k) personnel shortage, or the lack of specific expertise within the team, and l) an inefficient working environment due to internal dependencies or organisational bureaucracy.

Suggested mitigating measures.
As opposed to the identified factors contributing to operational pressure, several practical measures were mentioned that are used to prevent or mitigate work stress.These are: a) specific selection requirements for new employees, b) proper training, c) people-centred planning (to ensure an optimal workload and a healthy work-life balance), d) confined responsibility (to decrease the number of operational responsibilities) and e) investment in a socially safe working environment.

The SHP Framework
Parallel to the research on operational pressure, the general effects of human performance on safety were studied.Both safety and human performance are essential concepts within various domains, especially those that are safety-critical or involve specific hazards that need to be identified and mitigated.A comprehensive framework on the different factors at play could be very beneficial for different professional sectors.
For that reason, in this second line of research, a SHP framework was developed, applicable to a wide range of cases within different domains.The framework could serve as a starting point to a) analyse operational safety and human factors in relation to each other, b) identify actionable mitigations, and c) identify means to monitor operator performance, training effectiveness and safety outcomes.

Development of the framework
The SHP framework was designed in two phases.First, a group of seven experts on safety and human performance from the Netherlands Aerospace Centre (NLR) determined the main aspects of both human performance and safety that were deemed essential to be included in the framework.These concepts were then placed in a general overview with broad categorizations.This initial framework formed the basis for a further literature study on both existing human performance and safety frameworks and concepts.
Based on the information found in the research literature, further changes were made to the framework by a) specifying components (Human Being became Human (Well)being), b) adding additional components (the component Time surfaced as an important influence within the operational environment), c) merging components (Physical Capacity and Physical Fitness together became Physical Health), and d) splitting components into separate parts (the former component Organisational was divided into five different components).This resulted in the final SHP framework, as visualised in Figure 1.For a full overview of the literature used, please consult Minnema, Marsman and Wever (2023).

The finalised framework
The final framework (Figure 1) comprises five categories of factors that influence the outcomes in terms of performance and safety.These overarching categories are coloured green (or yellow if it is an uncontrollable factor), the subcomponents are coloured blue and the outcomes are coloured grey.
The separate categories and concepts are explained in further detail in a different report (Minnema et al., 2023) that serves as the framework's manual, including instructions on how the framework should be used.Nevertheless, the following paragraphs aim to describe the framework's components on a high level.First, Environment includes all aspects that relate to the environment in which humans operate and that can be influenced to a certain extent by the human operators themselves.These include the equipment used (i.e.aircraft avionics, furnishings, instruments, etc.), the physical work environment (ergonomic characteristics of workspaces such as the cockpit), human-machine interaction between the operator and the equipment interface, and the time in which the operation needs to take place.
Second, there is Human Competency, which relates to the set of characteristics that prepare and enable human operators to perform their duties safely.Important considerations are the human operator's personality characteristics (which link to for example risk-taking and safety behaviour), their training record, their KSA, their individual resilience, the motivation to complete a certain task to a certain standard, their ability and willingness to communicate with other relevant people and parties and the cognitive capacity they have available for the task.Due to the elaborate nature of the concept, workload is not individually mentioned in the framework, but it links well to this category.
Third, under the category Organisation, all aspects relating to organised groups of people are included.An organisation's culture affects how its employees complete a safety-critical task, but leadership and the scheduling of duty periods are also crucial.Moreover, clear distinction and knowledge of roles and tasks and operating procedures are important.
Finally, the fourth category Human (Well)being focuses on the individual, irrespective of the context in which they operate.There, the physical and mental health are considered just as the possibility to have a healthy work-life balance.

Resulting outcomes.
Importantly, the final main outcomes are both Performance and Safety, which describe how all human performance measures together lead to an outcome in performance and safety.Before such an outcome can happen, the aforementioned categories all lead to a human operation to be aware of a situation.This awareness is linked to the understanding of that same situation.Importantly, an operator can be aware of something without fully understanding it or its consequences, hence the specific separation is made in the SHP framework between awareness and understanding.To fully understand a situation, complete, correct and unambiguous information needs to be presented to the human operator at the right time and in such a way that the operator can take in that information.Then, based on the understanding the operator has of the situation, they decide to either act in a specific way or simply not act at all.

How to use the SHP framework
The SHP framework can be used as a starting point to analyse professional situations and identify possible courses of action.It is designed to cover all human performance aspects related to safety in a wide variety of sectors.However, each situation and professional use case is different.This is why the SHP framework can be tailored to a specific case.It may, for example, be possible that some of the subcomponents are irrelevant in certain situations.It is nevertheless recommended to go through all descriptions before deciding on whether a component is relevant for the current case or not.All relevant components can then be included, and if desired rephrased, while all irrelevant components can then be discarded.Then, as a final step, all relevant components can then be restructured in the general format of the SHP framework to provide a final overview of all-important considerations for that case.The following chapter provides an example of how to use the SHP framework.

Combining Two Lines of Research
The SHP framework specifically aims to analyse any human factors case in relation to safety outcomes.To provide an example of such an application, the issue of Operational Pressure within the aviation sector is used.

The application of Operational Pressure to the SHP Framework
The operational pressures as discussed in Section 2 were structured using the SHP framework, as visualised in Figure 2. A few changes were made for clarity.First, both the green and clear blue boxes are highlighted as components that are of specific relevance for the case of operational pressure in aviation; the green ones are discussed in the following paragraph.The grey boxes were originally part of the SHP framework but were deemed to be irrelevant as determined by both the literature study and interviews.The light blue boxes are components added to the framework, as these reflect important specific factors related to operational pressure that were not separate components in the original framework but do require additional focus.Please consult Minnema et al. (2023) for further explanations on the framework and how to use it.
Since these operational pressures do not influence someone's awareness, understanding, decisions or actions per se, but do affect their stress levels, "stress" is used as the outcome variable in this use case of the SHP framework.

A detailed view.
The factors identified in Section 2 to influence operational pressure are incorporated into the separate components of the SHP framework (Figure 2).While all highlighted boxes are relevant, the components Time, Training, and Knowledge, Skills and Abilities are explained in more detail to provide an example of how these relate to operational pressure and work stress.
First, in the work environment, time pressure can be caused by factors such as tight budgeting and unrealistic deadlines and can lead a human operator to experience work stress and subsequently hasten procedures and actions that need to be completed.This was found both in research studies (Hashemian & Triantis, 2023;Palmer, et al., 2004) as well as in interviews with professionals in the aviation domain.Having too little time to complete any safety-critical task can already impact safety margins negatively, but the stress experienced by individuals may also further affect their ability to complete the task to the desired standard, furthering the negative impact on safety margins.
Second, in terms of human competency, both an operator's training and KSAs can impact the level of work stress that the individual experiences.Training of all personnel needs to reflect the technological changes the aviation sector is subjected to.Not only basic, mechanical knowledge of the aircraft is required, but also information on different modes and settings is needed due to the fly-by-wire nature of modern aircraft.Due to the implementation of the autopilot and other sophisticated flight systems, pilots spend substantially more time simply monitoring the state and the modes of the aircraft instead of actual manual flying.This change is also reflected in the KSAs needed to be a successful pilot.As the nature of flying a modern aircraft seems to be evolving similarly, issues arise when a pilot does not feel competent because they lack certain knowledge, skills or attitude to do their job, as they likely feel more stressed.This may be especially true for more experienced pilots who have considerable flight hours in older aircraft that perhaps require more than two flight crew in the cockpit.While all pilots are assessed on their KSAs and undergo rigorous training before moving to other, or more advanced aircraft types, some pilots will never be able to successfully transfer.Moreover, with future operational definitions moving to a larger role of technology and automation, and perhaps even to single-pilot operations (SPO), there are likely to be further substantial changes in a pilot's tasks, communications and experiences on the flight deck, and thus in the training and KSAs required (Bailey et al., 2017).

Example of a final analysis
As predicted in Section 3.3 (How to use the SHP framework), not all of the framework's subcomponents were found in the research on operational pressure.The physical work environment and operating procedures, for example, were not identified as contributing factors to work stress.Some of the subcomponents as identified in the SHP framework, however, appear to manifest in a specific way in the aviation sector.For example, the equipment used to perform their task was identified as an influencing factor on work stress when this equipment was inadequate or unavailable.On another note, the operator's personality was not directly relevant to work stress, but their self-induced pressure was.Therefore, a revision of the SHP framework was made for the case of operational pressure.This revised framework is visualised in Figure 3.

Structuring mitigations of Operational Pressure with the SHP framework
While the most important components of the SHP framework in the application of operational pressure have been highlighted in the section above, mitigations to the pressures discussed should not be forgotten, as simply analysing an issue is meaningless if no further action is taken to use the findings from that initial step.Thus, the SHP framework can provide insights into which human performance areas similarly require special attention as the steps taken above.The highlighted areas in one's initial analysis of the case at hand give an indication of which topics require preventive or mitigation measures to reduce the impact of the pressures on the human operator, their performance, and safety in general.However, before mitigations can be put into place, a problem needs to be sufficiently diagnosed.While something may seem like a pressure, it needs to be confirmed with either scientific or field research to ensure that valuable time and effort only go into pressures that are actually sufficiently limiting to the human operator and to mitigations that are proven to be effective in reducing the effect of the pressure under consideration.While in the case of operational pressure many issues and many mitigations can be mentioned and analysed, it is beyond the scope of the present paper.

Conclusion
Specific developments within the aviation domain, such as increasing digitalisation, a push for sustainability and more congested airspace, will continue to put pressure on the human operator.Yet, these changes are just the tip of the iceberg as the more everyday issues also keep causing operational pressure.It is easy to lose the overview of all the pressures a human operator is subjected to, and even more importantly, the effects they have.Therefore, the SHP framework is a useful tool to get an overview of the current situation and to identify possible measures to mitigate or prevent the negative impact these immense pressures can have on humans.

Figure 2 .
Figure 2. Operational pressure visualized within the SHP framework.

Figure 3 .
Figure 3. Adaptation of the SHP framework to the case of operational pressure.