Mica R. Endsley

Toward a Theory of Situation Awareness in Dynamic Systems

This paper presents a theoretical model of situation awareness based on its role in dynamic human decision making in a variety of domains. Situation awareness is presented as a predominant concern in system operation, based on a descriptive view of decision making. The relationship between situation awareness and numerous individual and environmental factors is explored. Among these factors, attention and working memory are presented as critical factors limiting operators from acquiring and interpreting information from the environment to form situation awareness, and mental models and goal-directed behavior are hypothesized as important mechanisms for overcoming these limits. The impact of design features, workload, stress, system complexity, and automation on operator situation awareness is addressed, and a taxonomy of errors in situation awareness is introduced, based on the model presented. The model is used to generate design implications for enhancing operator situation awareness and future directions for situation awareness research.

MEASUREMENT OF SITUATION AWARENESS IN DYNAMIC SYSTEMS

Methodologies for the empirical measurement of situation awareness are reviewed, including a discussion of the advantages and disadvantages of each method and the potential limitations of the measures from a theoretical and practical viewpoint. Two studies are presented that investigate questions of validity and intrusiveness regarding a query-based technique. This technique requires that a simulation of the operational tasks be momentarily interrupted in order to query operators on their situation awareness. The results of the two studies indicate that the query technique is not intrusive on normal subject behavior during the trial and does not suffer from limitations of human memory, which provides an indication of empirical validity. The results of other validity studies regarding the technique are discussed along with recommendations for its use in measuring situation awareness in varied settings.

DESIGN AND EVALUATION FOR SITUATION AWARENESS ENHANCEMENT

Situation awareness (SA) is an important component of pilot/system performance in all types of aircraft. It is the role of the human factors engineer to develop aircraft cockpits which will enhance SA. Research in the area of situation awareness is is vitally needed if system designers are to meet the challenge of providing cockpits which enhance SA. This paper presents a discussion of the SA construct, important considerations facing designers of aircraft systems, and current research in the area of SA measurement.

Situation Awareness Analysis and Measurement

Contents: Preface. Part I: Introduction and Overview. M.R. Endsley, Theoretical Underpinnings of Situation Awareness: A Critical Review. R.W. Pew, The State of Situation Awareness Measurement. Part II: Measurement Approaches. G. Klein, Analysis of Situation Awareness From Critical Incident Reports. M.D. Rodgers, R.H. Mogford, B. Strauch, Post Hoc Assessment of Situation Awareness in Air Traffic Control Incidents and Major Aircraft Accidents. D.G. Jones, Subjective Measures of Situation Awareness. H.H. Bell, D.R. Lyon, Using Observer Ratings to Assess Situation Awareness. M.R. Endsley, Direct Measurement of Situation Awareness: Validity and Use of SAGAT. G.F. Wilson, Strategies for Psychophysiological Assessment of Situation Awareness. A.R. Pritchett, R.J. Hansman, Use of Testable Responses for Performance-Based Measurement of Situation Awareness. C.D. Wickens, The Trade-Off of Design for Routine and Unexpected Performance: Implications of Situation Awareness. M.A. Vidulich, Testing the Sensitivity of Situation Awareness Metrics in Interface Evaluations. Part III: Special Topics in Situation Awareness. L.J. Gugerty, W.C. Tirre, Individual Differences in Situation Awareness. C.A. Bolstad, T.M. Hess, Situation Awareness and Aging. W. Shebilske, B.P. Goettl, D.J. Garland, Situation Awareness, Automaticity, and Training. C. Prince, E. Salas, Team Situation Awareness, Errors, and Crew Resource Management: Research Integration for Training Guidance. M.R. Endsley, M.M. Robertson, Training for Situation Awareness in Individuals and Teams.

Situation awareness global assessment technique (SAGAT)

Pilot-vehicle interface designs must be driven by the gaol of establishing and maintaining high pilot situation awareness. The situation-awareness global assessment technique (SAGAT), developed to assist in this process by providing an objective measure of pilots situation awareness with any given aircraft design, is described. SAGAT is considered to represent a substantial improvement in the evaluation of pilot-vehicle interface designs, facilitating the development of cockpits which assist the pilot in surviving combat. A formal definition of situation awareness is presented a description of the SAGAT methology and a discussion of its validation.<<ETX>>

The effects of level of automation and adaptive automation on human performance, situation awareness and workload in a dynamic control task

This paper extends previous research on two approaches to human-centred automation: (1) intermediate levels of automation (LOAs) for maintaining operator involvement in complex systems control and facilitating situation awareness; and (2) adaptive automation (AA) for managing operator workload through dynamic control allocations between the human and machine over time. Some empirical research has been conducted to examine LOA and AA independently, with the objective of detailing a theory of human-centred automation. Unfortunately, no previous work has studied the interaction of these two approaches, nor has any research attempted to systematically determine which LOAs should be used in adaptive systems and how certain types of dynamic function allocations should be scheduled over time. The present research briefly reviews the theory of human-centred automation and LOA and AA approaches. Building on this background, an initial study was presented that attempts to address the conjuncture of these two approaches to human-centred automation. An experiment was conducted in which a dual-task scenario was used to assess the performance, SA and workload effects of low, intermediate and high LOAs, which were dynamically allocated (as part of an AA strategy) during manual system control for various cycle times comprising 20, 40 and 60% of task time. The LOA and automation allocation cycle time (AACT) combinations were compared to completely manual control and fully automated control of a dynamic control task performed in conjunction with an embedded secondary monitoring task. Results revealed LOA to be the driving factor in determining primary task performance and SA. Low-level automation produced superior performance and intermediate LOAs facilitated higher SA, but this was not associated with improved performance or reduced workload. The AACT was the driving factor in perceptions of primary task workload and secondary task performance. When a greater percentage of primary task time was automated, operator perceptual resources were freed-up and monitoring performance on the secondary task improved. Longer automation cycle times than have previously been studied may have benefits for overall human–machine system performance. The combined effect of LOA and AA on all measures did not appear to be ‘additive’ in nature. That is, the LOA producing the best performance (low level automation) did not do so at the AACT, which produced superior performance (maximum cycle time). In general, the results are supportive of intermediate LOAs and AA as approaches to human-centred automation, but each appears to provide different benefits to human–machine system performance. This work provides additional information for a developing theory of human-centred automation.

Situation Awareness Misconceptions and Misunderstandings

Situation awareness (SA) has become a widely used construct within the human factors community, the focus of considerable research over the past 25 years. This research has been used to drive the development of advanced information displays, the design of automated systems, information fusion algorithms, and new training approaches for improving SA in individuals and teams. In recent years, a number of papers criticized the Endsley model of SA on various grounds. I review those criticisms here and show them to be based on misunderstandings of the model. I also review several new models of SA, including situated SA, distributed SA, and sensemaking, in light of this discussion and show how they compare to existing models of SA in individuals and teams.

Design of Automation for Telerobots and the Effect on Performance, Operator Situation Awareness, and Subjective Workload

In this article we review and assess human-centered level of automation (LOA), an alternate approach to traditional, technology-centered design of automation in dynamic-control systems. The objective of human-controlled LOA is to improve human-machine performance by taking into account both operator and technological capabilities. Automation literature has shown that traditional automation can lead to problems in operator situation awareness (SA) due to the out-of-the (control) loop performance problem, which may lead to a negative impact on overall systems performance. Herein we address a standing paucity of research into LOA to deal with these problems. Various schemes of generic control system function allocations were developed to establish a LOA taxonomy. The functions allocated to a human operator, a computer, or both, included monitoring system variables, generating process plans, selecting an “optimal” plan and implementing the plan. Five different function allocation schemes, or LOAs, were empirically investigated as to their usefulness for enhancing telerobot system performance and operator SA, as well as reducing workload. Human participants participated in experimental trials involving a high fidelity, interactive simulation of a telerobot performing nuclear materials handling at the various LOAs. Automation failures were attributed to various simulated system deficiencies necessitating operator detection and correction to return to functioning at an automated mode. Operator performance at each LOA, and during the failure periods, was evaluated. Operator SA was measured using the Situation Awareness Global Assessment Technique, and perceived workload was measured using the NASA-Task Load Index. Results demonstrated improvements in human-machine system performance at higher LOAs (levels involving greater computer control of system functions) along with lower operator subjective workload. However, under the same conditions, operator SA was reduced for certain types of system problems and reaction time to, and performance during, automation failures was substantially lower. Performance during automation failure was best when participants had been functioning at lower, intermediate LOAs (levels involving greater human control of system functions).

On the Design of Adaptive Automation for Complex Systems

This article presents a constrained review of human factors issues relevant to adaptive automation (AA), including designing complex system interfaces to support AA, facilitating human–computer interaction and crew interactions in adaptive system operations, and considering workload associated with AA management in the design of human roles in adaptive systems. Unfortunately, these issues have received limited attention in earlier reviews of AA. This work is aimed at supporting a general theory of human-centered automation advocating humans as active information processors in complex system control loops to support situation awareness and effective performance. The review demonstrates the need for research into user-centered design of dynamic displays in adaptive systems. It also points to the need for discretion in designing transparent interfaces to facilitate human awareness of modes of automated systems. Finally, the review identifies the need to consider critical human–human interactions in designing adaptive systems. This work describes important branches of a developing framework of AA research and contributes to the general theory of human-centered automation.

Situation awareness in aircraft maintenance teams

Abstract Research was conducted at a major airline to investigate factors related to situation awareness in aviation maintenance teams. Situation awareness has been found to be critical to performance and error prevention in many environments. Its role in the maintenance domain for the performance of both individuals and teams is discussed. Situation awareness requirements for aviation maintenance were determined as well as the technologies and personnel resources used to achieve situation awareness. Barriers and problems for situation awareness both across and within teams involved in aviation maintenance were revealed. Based on this analysis, recommendations for the development of a training program to improve situation awareness in aircraft maintenance at the individual and team level are presented. Relevance to industry The importance of situation awareness for preventing errors in maintenance is discussed as well as factors that contribute to problems with situation awareness across multiple teams. Specific recommendations for improving situation awareness through organization and system design and through training are made that are applicable to a wide variety of industrial settings.