Abstract
BACKGROUND:
Situational awareness is the acquisition of information from elements present in the work environment, the perception of the meaning of this information, and the prediction of future working conditions. Sleepiness and fatigue can influence an individual’s ability to reach situation awareness, decision-making, and performance on a task.
OBJECTIVE:
This scoping review examines methods used to assess situational awareness, fatigue, sleepiness, and their interrelationships.
METHODS
A systematic search of online databases was conducted to identify experimental, peer-reviewed articles published in English between 2017 and 2022. A total of 29 publications were selected for analysis.
RESULTS:
The selected studies originated from various countries, primarily in the northern hemisphere. Health and automotive engineering were the academic categories with the highest publications. The studies employed objective and subjective methods to assess situational awareness, fatigue, and sleepiness.
CONCLUSIONS:
Most studies reported a decline in situational awareness during fatigue and sleepiness conditions, although one study did not find this association. Future research should focus on employing objective methods to analyze cognitive factors, increasing sample sizes, and conducting testing in real-world situations.
Introduction
Situational awareness (SA) is a factor that can contribute to human error and is directly associated with the activity’s success [1]. SA encompasses awareness of the current environment and categorizes it into three levels: perception (Level 1), comprehension (Level 2), and projection (Level 3). Level 1 relates to the perception of information from the environment acquired by any of the five senses. Level 2 interprets the information perceived in Level 1 and its importance to the situation. Level 3 involves anticipating how the perceived information will impact future events. Considering the three levels, Level 1 is the most important, as it is the basis for achieving the other levels [2]. It is important to note that SA serves as the basis for decision-making rather than being the decision-making process itself [3]. Stanton et al. conclude that “loss of situational awareness is correlated with poor system performance. People who have lost situational awareness may be slower to detect problems with the system they are controlling as well as requiring additional time to diagnose problems and conduct remedial activities when they are finally detected [4].”
SA demands high levels of cognitive functioning. However, sleep and fatigue can hinder achieving SA levels and impact decision-making and activity performance [5]. Sleep is an essential physiological process that allows the body to renew its physical and mental capacities, enabling the individual to reach higher levels of awareness. On the other hand, individuals who experience insufficient or poor-quality sleep may struggle to restore their self-control abilities, leading to unsafe behaviors [3]. Sleep loss, a reduction in the hours of sleep from the recommended levels, may occur due to sleep deprivation, restriction, or disruption [5]. Sleep deprivation can reduce alertness, attention, concentration, memory, and decision-making. Functions such as working and long-term memory, visual attention, and decision-making are necessary for achieving higher levels of SA [6].
Fatigue and sleepiness are usually used as synonymous [7]. According to the International Civil Aviation Organization (ICAO), 2019, fatigue is “ a physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase, and/or workload (mental and/or physical activity) that can impair a person’s alertness and ability to perform safety related operational duties [8].” Thus, sleepiness is one of the causes of fatigue. Other factors that contribute to the development of mental fatigue are working time and mental workload [9]. Fatigue can decrease attention and vigilance, delay cognitive processing, alter safety awareness, and influence the ability to achieve SA levels [6, 10]. As stress and fatigue increase, there is a decrease in SA levels, which increases unsafe behavior and the risk of accidents [11, 12].
Sleep loss, sleep deprivation, and fatigue are potential risks to health and safety. Therefore, more information about the relationships and consequences of sleepiness and fatigue on situational awareness is needed. Thus, this study aimed to perform a scoping review to systematically map studies that experimentally assess sleepiness, fatigue, and situational awareness. The study evaluated the main methodologies employed in previous research to assess sleepiness, fatigue, and situational awareness, while also identifying gaps in knowledge.
Methods
This study conducted a scoping review of the published scientific literature on situational awareness, fatigue, and sleepiness. The study design adhered to the guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [13]. This study is exempt from Institutional Review Board approval as a literature review.
This scoping review incorporates full articles published in peer-reviewed journals, written in English, and published from 2017 until 2022. The selection process involved utilizing keywords such as “situation awareness” or “situational awareness” in conjunction with “fatigue” or “sleep.” The review included experimental studies that objectively or subjectively assessed the relationship between situational awareness and fatigue or situational awareness and sleepiness. Excluded from the review were review articles, abstracts, and studies that solely evaluated situational awareness or fatigue and situational awareness or sleepiness.
Three databases, namely Scopus, Web of Science, and PubMed were used to conduct the article search. The survey was conducted between October 25 and November 3, 2022. All the articles were compiled into a table, and the duplicates were removed. Initially, the articles were sorted based on their title and abstract, and subsequently, the full texts were examined to determine whether they met the inclusion and exclusion criteria. The two authors collaborated in conducting the search and article screening process for this scoping review. They employed a systematic approach, utilizing pre-established inclusion and exclusion criteria to identify relevant articles. In instances of disagreement regarding study selection and data extraction, consensus was achieved through thoughtful discussions between the authors. Only articles that received agreement from both authors were included in this review. This cooperative approach guaranteed a thorough and meticulous screening of pertinent publications for review.
The data charting process involved extracting relevant information from the included sources of evidence and organizing it into a structured data summary table. This table included details such as the publication year, country, journal, academic categories, population, methods used to assess situational awareness, fatigue, sleepiness, strengths, and weaknesses, as well as the results and limitations of each study. Following the data charting, the studies were categorized based on the methods employed to evaluate situational awareness, fatigue, and sleepiness, specifically objective and subjective methods.
Results
The search of three databases had initially identified 298 papers. After removing the duplicates total of 138 were analyzed. Out of the total articles reviewed, 109 articles were excluded for the following reasons: 74 articles did not evaluate situational awareness, fatigue, or sleepiness; 18 articles were not experimental research; 3 articles were not full-length articles, and five articles were unable to be retrieved. As a result, 29 articles met the eligibility criteria for the systematic study. Figure 1 provides a visual representation of the research flow diagram.

Flow diagram.
The 29 papers included in the study were conducted in 21 countries. Among them, four articles originated from the USA [5, 14–16]. Five countries contributed two articles each: Germany, [7, 17], India, [18, 19], Korea, [20, 21] Ireland, [22, 23] and Italy [24, 25]. The rest of the countries made one paper each: Australia [26], Belgium [27], Canada [28], China [29], Denmark [30], France [31], Ghana [32], Indonesia [6], Iran [3], New Zealand [33], Norway [11], Philippines [34], Puerto Rico [35], Slovakia [36], and the United Kingdom [37].
The study classified the 29 articles into ten academic categories. Figure 2 illustrates the distribution of these categories. Among the articles, eight were related to Health [16, 36], while seven assessed automotive engineering [6, 29]. Four articles focused on Aeronautics [22, 35], two articles on maritime transport [11, 27], and one article on aerospace [5]. Additionally, two articles were related to agriculture [15, 37], two articles to industrial organization [3, 25], one article to computer engineering [19], one article to robotics [14], and one article to transport engineering [28].

Distribution of academic categories.
The papers included in the range had varying population sizes, ranging from 4 to 601. Like the academic categories, the population also varied. Health studies analyzed physicians [31–33, 36], nurses [26, 36], paramedics [36], and soccer student-athletes [16]. The population of automotive engineering was composed of truck drivers [7] and common drivers [17, 29], as well as students [6]. In the aeronautics category, air traffic management officers [34], and commercial airline pilots were assessed in the aeronautics category [23]. The analyzed aerospace population consisted of volunteers trained on SPHERE [5] and maritime engineering employees from the maritime industry [27]. In the agricultural sector, the study included farmers, agricultural stakeholders [37], and professional loggers [15]. The population of the industrial organization comprised workers from various industries [3, 25]. In Robotics, university students were surveyed [14] and in transport engineering, locomotive crew [28]. Some papers did not specify the population analyzed, referring to them as non-pilot volunteers [22], participants [24], and working individuals [19]. Two articles analyzed teams of professionals, such as health teams managing newborns [30], and the National Transportation Safety Board (NTSB) [35].
This study focused on three main categories: Situation awareness, Fatigue, and Sleepiness. The evaluation method of each category was analyzed in all papers. Each category’s evaluation method was analyzed in all papers, categorized as objective or subjective. Objective evaluation of situation awareness utilized the following method subcategories: Behavior observation [17, 37], coded archival research [35], eye-tracking glasses [7, 18], and quantitative analysis of situation awareness [5, 34]. To assess subjective situation awareness, the method subcategories were: questionnaires [3, 36], and semi-structured interviews [15, 27].
The method subcategories for evaluating objective fatigue included behavior observation [16, 37], coded archival research [35], psychomotor vigilance task (PVT) [22, 33], and physiological sensors [11, 14]. Subjective fatigue, on the other hand, was assessed through questionnaires [3, 36], and semi-structured interviews [15, 27].
The objective methods subcategories o analyze sleepiness were with physiological sensors [5, 23]. The subjective sleepiness method subcategories were questionnaires [3, 33], and sleep logs [5, 23].
For data collection, ten studies used simulators [5, 33], and two studies used scenarios [31, 37]. For sleepiness and fatigue assessment, seven studies subjected participants to sleep deprivation [6, 33].
The authors, country of origin, academic categories, population, and methods of the studies are presented in Table 1. The quality of the selected articles in the review was assessed based on the strengths and weaknesses of the methodology employed in each article. Table 2 represents this evaluation.
Characteristics of the study
Paper’s strengths and weaknesses
Situational awareness involves obtaining existing information in the work environment, perceiving the meaning of this information, and predicting future working conditions [3]. The methods used to assess situational awareness in the included articles were categorized as objective and subjective. Table 3 presents the methods employed in each article.
Situation awareness assessment
Situation awareness assessment
Anesthetists’ Non-Technical Skills (ANTS) employ a graded scale with four categories to assess performance, which two anesthetists observe via video [31]. AeroNOTS is an adaptation of ANTS, assessing clinical performance in situation awareness, task management, decision-making, and teamwork [33].
The go/no-go scenario involves participants choosing to continue or halt a task related to cattle handling, explaining their reasoning and risk management strategies [37].
Observation of facial, ocular, and behavioral indicators was used to evaluate drivers’ behavior in automated driving, including reaction times, glancing behavior, and responses to risky situations [17, 29].
Data was recorded in real-time to assess security guards’ alertness levels and locomotive crew members’ response to train control signals [19, 28].
Video analysis and the Global Assessment of Team Performance (GAOTP) checklist assessed labor non-technical skills and team performance [30].
Coded archival research analyzed crew behavior using air accident files to evaluate situational awareness. Phrases like “I do not know why” and “I do not know what is going on” are examples of not being aware [35].
The eye-tracking glasses have a camera to record what the individual sees and infrared cameras that evaluate the driver’s pupils to detect the gaze. The eye-tracking glasses measured situational awareness through glance behavior [7, 18].
Situational Awareness Questions: SA was assessed by asking questions over 5 seconds at specific points during the flight. Awareness of speed, location, altitude, and TCAS (Traffic Avoidance Collision System) static images were evaluated [23]. In another study, SA questions included the perception of each SPHERES’ initial and final position, movement, and fuel consumption [5]. During practice, student-athletes were required to close their eyes, indicate other players’ positions, and estimate the distance between them. SA was measured by assessing the actual and estimated distance between athletes [16].
Situational awareness was assessed through speed, location, perception, and estimation questions in various scenarios [5, 23].
SPAM involves measuring SA through online questions administered randomly to participants [34]. QASA employs a freezing technique, challenging participants to assess their car’s speed, compare it with the vehicle ahead, and estimate the time required to reach it [6]. SASHA is a questionnaire designed to gauge SA in aircrews [34]. SART is a subjective tool developed for assessing SA in pilots, consisting of attention supply, attention demand, and task comprehension items [14].
The Kano Questionnaire incorporates functional and dysfunctional questions to categorize acceptance elements into different dimensions [21]. Likert scale questionnaires assess SA in work environments, employing scales to measure factors like awareness, event recording, and response to COVID-19 risks [3, 32]. The SAPH@W questionnaire adopts a ten-point scale to evaluate SA by addressing specific risks in participants’ work environments [24].
The work situation awareness scale comprises 20 items and utilizes factor analysis to identify subscales related to SA [36]. The NTSC-Q questionnaire employs behavioral indicators such as risk identification and situational monitoring to assess SA [25].
Lastly, semi-structured interviews provide qualitative insights into SA, with participants sharing experiences and perceptions through graded responses and open-ended questions. These varied methods and instruments contribute to a comprehensive understanding of SA across different domains, enabling researchers and practitioners to enhance awareness and decision-making processes [15, 27].
Fatigue is characterized as a decrease in cognitive and physical performance resulting from prolonged exertion, sleep deprivation, and interruption of the internal clock [25]. Measures for assessing fatigue in the articles were divided into objective and subjective. Table 4 shows the method utilized in each paper.
Fatigue assessment
Fatigue assessment
In the go/no-go scenario, participants are exposed to scenarios involving cattle handling. They are required to decide whether to proceed with the task, explain their choice, and outline their risk management strategies [37].
Observation of facial, ocular, and behavioral indicators involves analyzing facial points to detect blinking and examining signs of fatigue, such as prolonged eyelid closure, yawning, and facial rubbing [17, 29].
The Global Assessment of Team Performance Checklist (GAOTP) is a validated tool to assess team performance in non-technical skills. It considers various factors such as the team’s environment, the voices of team members, and indications of stress or fatigue [30].
In coded archival research, researchers analyze air accident files to evaluate crew behavior and identify indications of sleep deprivation, shift work, speech errors, or yawning [35].
During performance under pressure and fatigue, athletes exert themselves physically and mentally in activities like speed and precision competitions, which can result in fatigue [16].
Electrocardiogram (ECG) signals are collected to analyze heart rate variability (HRV) features, reflecting the impact of fatigue on parasympathetic activity [11, 14]. Electromyogram (EMG) is employed to study muscle contraction variations during operational activities, which tend to decrease in the presence of fatigue [11]. Additionally, body temperature sensors monitor fluctuations related to the circadian rhythm, indicating fatigue [11].
The Psychomotor Vigilance Task (PVT) involves participants performing a task that assesses attention and fatigue by quickly responding to visual stimuli on a computer screen. Mean reaction time (MRT) and attention lapses are analyzed [22, 33].
The Fatigue Scale-14 (FS-14) is employed to subjectively evaluate individual fatigue levels and monitor fatigue cases in epidemiological studies [29]. The Fatigue level experienced participants assess their level of fatigue on a scale ranging from low to high after completing an activity [14]. The Fatigue Severity Scale (FSS) is a practical tool known for its high internal consistency and good test-retest reliability, used to measure subjective fatigue [14]. Additionally, the Samn-Perelli Fatigue Scale, consisting of seven items, specifically targets fatigue in military air transport [23, 33].
The Kano questionnaire evaluates acceptance elements and categorizes them into distinct dimensions [21]. The Maslach Burnout Inventory General Survey involves participants rating their responses on a five-point scale to assess emotional exhaustion experienced in the workplace [32]. The Safety at Work (SAPH@W) questionnaire employs a ten-point scale to gauge the effectiveness of strategies for managing physical fatigue and related factors [24]. A subjective measure of fatigue, the fatigue assessment scale consists of ten items that are graded on a five-point scale [36]. The NTSC-Q questionnaire assesses behavioral indicators of fatigue, coping strategies, and sources of stress [25]. Lastly, the Occupational Fatigue/Exhaustion Recovery (OFER) scale employs a six-point Likert scale to evaluate various types of fatigue, including severe, chronic, and shift work fatigue [3, 33].
In semi-structured interviews, participants share their experiences of fatigue by responding to questions and rating their responses on a five-point scale. They also have the opportunity to provide open-ended answers [15, 27]. These interviews aim to identify and explore fatigue categories, such as competing demands, fatigue, and stress [26].
Sleep loss can lead to reduced performance, learning, and short-term working memory, leading to increased accidents and errors [5]. Table 5 shows the method utilized in each paper.
Sleepiness assessment
Sleepiness assessment
Actigraphy is a wearable device like a smartwatch or a smart ring that assesses daily sleep patterns, total sleep time, sleep efficiency, and wake frequency after sleep onset [5, 23].
Eye-tracking glasses provide objective measures of alertness, including pupil diameter, blink frequency, and blink duration [18]. Electroencephalography (EEG) detects brain electrical waves to differentiate sleep stages and measure cognitive workload [20]. Galvanic skin response (GSR) evaluates sweating as an indicator of participant arousal [20]. Electrocardiogram (ECG) signals assess heart rate variation and participant excitement/alertness [20].
The Karolinska sleepiness scale (KSS) and Epworth sleepiness scale (ESS) are subjective scales that rate sleepiness levels [3, 33]. The Pittsburgh Sleep Quality Index (PSQI) is a subjective questionnaire assessing sleep quality and disturbances over a month [33].
Sleep logs involve participants keeping records of their sleep hours and quality [5, 23].
The present scoping review focused on analyzing experimental studies on situation awareness, fatigue, and sleepiness. These studies were conducted in 21 countries, with the highest production observed in the USA. Most studies were conducted in the Northern Hemisphere, and none were conducted in South America.
Regarding academic categories, eight studies were related to Health, and five specifically evaluated non-technical skills (NTS). NTS encompasses social and mental skills crucial for effective and safe task performance [38]. These skills include leadership, situational awareness, communication, teamwork, decision-making, and coping with stress and fatigue [30]. NTS are considered tacit rather than technical skills and play a fundamental role in incident control. They find application in various work situations as they are more general and less specific to a particular domain than technical skills [25]. Failures in NTS have been associated with accidents across different work environments [37]. Moreover, NTS can be influenced by fatigue [33]. The three main factors for coping with fatigue are recognizing the antecedents of fatigue, identifying the consequences of fatigue, and implementing coping strategies [25].
Seven articles were devoted to studying automotive engineering, focusing on automated driving. Automated driving may increase driver sleepiness and reduce situational awareness [7]. The introduction of automated driving systems allows drivers to relinquish active control, which, in turn, can result in reduced alertness. Notably, one of the primary challenges associated with highly automated vehicles revolves around ensuring that drivers can promptly assume control when necessary, taking into account considerations of situational awareness and safety [18]. In the context of automated driving, specific environmental conditions or road characteristics, such as heavy rain or roadworks, can adversely affect the performance of sensors and object recognition, thereby necessitating driver intervention [17]. Consequently, when drivers are required to regain control, it becomes crucial for them to allocate sufficient time for reestablishing situational awareness and physically preparing themselves [29].
Situation awareness and fatigue/sleepiness
Sleepiness and fatigue are common among the population studied in the papers, yet their impact on performance remains uncertain. The relationship between sleep loss, situational awareness, and non-technical skills (NTS) remains unknown [31]. Sleep loss can influence an individual’s ability to achieve optimal levels of situational awareness, decision-making, and task performance. Moreover, individuals may overestimate their situational awareness when experiencing sleep loss or food deprivation compared to expert assessments [5].
Several papers have shown that fatigue and sleepiness impact situational awareness. Mohammadfam et al. revealed a negative correlation between fatigue and situational awareness, where an increase in sleepiness results in a decline in situational awareness. Myers et al. demonstrated that tiredness decreases non-technical performance and situational awareness compared to well-rested individuals. Wijayanto et al. confirmed that sleep-deprived driving performance is significantly impaired due to reduced situational awareness. Vogelpohl et al. identified that drivers experiencing fatigue have difficulty achieving situational awareness and may face challenges in take-over requests situations. Bongo et al. provided evidence of an inverse relationship between fatigue and workload, which alters situational awareness. Moreover, fatigue is associated with various concerns related to the visual display terminal. Lastly, Sedlár demonstrated that higher stress levels and fatigue in the workplace lead to poorer situational awareness and reduced cognitive flexibility.
Although one paper does not demonstrate a significant impact of fatigue or sleepiness on situational awareness, O’Hagan et al. found no significant changes in situational awareness after 24 hours of sleep deprivation. The study utilized subjective methods to assess situational awareness. It is important to note that subjective measures may only reflect the participant’s perceived consciousness during the activity rather than their actual level of consciousness.
Studies limitations and gaps
The reviewed studies had limitations, including small sample sizes, disparities between simulated and real environments, and reliance on subjective analysis. Some studies also faced limitations related to subjective measures of cognitive abilities. It is important to note that findings from simulated conditions may not fully represent actual performance, and the configuration of driving simulators might have influenced the development of fatigue. Additionally, the absence of force feedback in the simulated environment and the closer monitoring in eye-tracking studies could affect participants’ behavior.
The study identified several gaps in the existing literature. Firstly, there is a need for more research conducted in South America to address the geographical gap in understanding situational awareness, fatigue, and sleepiness. Secondly, employing more objective methods to assess these factors is crucial, as objective measures provide more accurate and reliable data. Moreover, the limited sample sizes in many studies restrict the generalizability of the findings. Lastly, future research should include real-world testing to validate the results and ensure their practical relevance.
Future research should focus on utilizing objective measures, increasing sample sizes, conducting real-world testing, and further exploring the cognitive aspects of situational awareness, fatigue, and sleepiness. Addressing these gaps will contribute to a more comprehensive understanding of these factors and their impact on safety and performance in various domains.
This study had certain limitations. Firstly, while some studies have established a connection between fatigue, drowsiness, and situational awareness, further research is required to better establish this association in specific articles. Secondly, although some studies reported the analysis method used, providing additional explanations regarding the employed methodology would be beneficial.
Conclusion
This scoping review aimed to assess experimental studies focusing on situational awareness, fatigue, and sleepiness, highlighting several significant findings, and identifying critical gaps in the existing literature.
The results of the examined studies consistently indicated a reduction in situational awareness under conditions of fatigue and sleepiness, except for one study that did not establish this connection. This implies that both fatigue and sleepiness can have a substantial impact on an individual’s capacity to attain and sustain situational awareness, ultimately influencing their decision-making and task performance. Nevertheless, there is a need for further research to incorporate objective methodologies for the analysis of cognitive factors related to situational awareness.
While the reviewed studies offered valuable insights, they also unveiled several gaps. These gaps encompass the absence of research conducted in South America, the limited application of objective methods to evaluate situational awareness, fatigue, and sleepiness, the relatively small sample sizes within many of the reviewed studies, and the prevalence of studies conducted in simulated environments. These factors underscore the necessity for future research to prioritize studies in diverse geographical regions, the adoption of objective measures, the enlargement of sample sizes, the investigation of real-world scenarios, and a deeper exploration of the cognitive aspects related to situational awareness, fatigue, and sleepiness.
Addressing these gaps will enable researchers and practitioners to develop a more comprehensive understanding of situational awareness, fatigue, and sleepiness. This understanding will facilitate the development of effective interventions and strategies to enhance performance and safety across various domains, thereby improving the well-being and productivity of individuals in both professional and everyday life contexts.
Ethical approval
This study, as a literature review, is exempt from Institutional Review Board approval.
Informed consent
This study, as a literature review, is exempt from informed consent.
Conflict of interest
The authors declare that they have no conflict of interest.
Footnotes
Acknowledgments
The authors have no acknowledgments.
Funding
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior –Brasil (CAPES) –Finance Code 001.
