Accidents systems theory

At the present time, there is a fair understanding about the initiation of RPTs in various systems, but in some instances, particularly for metal-water accidents, the theory is poorly developed and untested in controlled laboratory experiments. The area of escalation of a small-scale RPT to a large, coherent explosion has been developed into a logical picture, but again proof tests on a large scale are not available. 

For accident mechanism theory, many domestic and foreign scholars and experts have done much research and put forward a lot of typical accident theory. Such as Domino accident model theory proposed by Heinrich in 1936, Energy transfer accident theory proposed by Gibson in 1961, then derived by Haddon in 1966, Gold mine accident model proposed by Lawrence in 1974, and so on. In domestic, Chen Baozhi put forward the two class of hazard point in 1995, Zhang Li put forward Human error accident model in Complex man-machine system in 1996, He Xueqiu put forward... 

The new model of accidents introduced in part II of this book incorporates the basic systems theory idea of hierarchical levels, where constraints or lack of constraints at the higher levels control or allow lower-level behavior. Safety is treated as an emergent property at each of these levels. Safety depends on the enforcement of constraints on the behavior of the components in the system, including constraints on their potential interactions. Safety in the batch chemical reactor in the previous chapter, for example, depends on the enforcement of a constraint on the relationship between the state of the catalyst valve and the water valve. 

Safety approaches based on systems theory consider accidents as arising from the interactions among system components and usually do not specify single causal variables or factors [112]. Whereas industrial (occupational) safety models and event chain models focus on unsafe acts or conditions, classic system safety models instead look at what went wrong with the system s operation or organization to allow the accident to take place. 

Systems theory provides a much better foundation for safety engineering than the classic analytic reduction approach underlying event-based models of accidents. It provides a way forward to much more powerful and effective safety and risk analysis and management procedures that handle the inadequacies and needed extensions to current practice described in chapter 2. 

STAMP AN ACCIDENT MODEL BASED ON SYSTEMS THEORY... 

In systems theory, emergent properties, such as safety, arise from the interactions among the system components. The emergent properties are controlled by imposing constraints on the behavior of and interactions among the components. Safety then becomes a control problem where the goal of the control is to enforce the safety constraints. Accidents result from inadequate control or enforcement of safety-related constraints on the development, design, and operation of the system. 

The STAMP (Systems-Theoretic Accident Model and Process) model of accident causation is built on these three basic concepts—safety constraints, a hierarchical safety control structure, and process models—along with basic systems theory concepts. All the pieces for a new causation model have been presented. It is now simply a matter of putting them together. 

This chapter starts with a discussion of the role of specifications and how systems theory can be used as the foundation for the specification of complex systems. Then an example of how to put the components together in system design and development is presented. Chapters 11 and 12 cover how to maximize learning from accidents and incidents and how to enforce safety constraints during operations. The design of safety information systems is discussed in chapter 13. 

The book is divided into three sections.The first part explains why a new approach is needed, including the limitations of traditional accident models, the goals for a new model, and the fundamental ideas in system theory upon which the new model is based. The second part presents the new, extended causality model. Ihe final part shows how the new model can be used to create new techniques for system safety engineering, including accident investigation and analysis, hazard analysis, design for safety, operations, and management. 

Accident causation theories include the human factors theory, the domino theory, the systems theory, the combination theory, the epidemiological theory, and the accident/inddent theory [1,2]. The first two of these theories are described below. 

Part II reviews some of the basic theories and principles in the design of SHE information systems. Thereafter, an accident model is introdnced that represents a synthesis of many existing models. It provides a framework for a presentation of the different types of methods and tools in Parts HI to V. Part II also introduces a number of theoretical concepts and principles including accident-barrier theory, theories on human performance and errors, and feedback mechanisms in decision-making. This part ends with a set of criteria for the evaluation of SHE information systems. 

According to Systems Theory, an accident is considered an abnormal effect of the system. The causes of the deviation from the desired state are defects in individual parts of a system, or in the interaction between them. Particular parts are commonly referred to as individual, task, equipment, and environment. Main emphasis is laid upon the development of aids and procedures to analyze errors, failures, hazards, and accidents and their interrelationships. 

Certain types of deviations within a man-machine system increase the probability of accidents and/or the expected value of loss due to accidents, thus being valid indicators of the accident risk. The nature of accidents represented by the deviation model is based on systems theory, on the energy exchange model, the multilinear events sequencing approach, and concepts of human errors as discussed in chapter 4. 

Both the integrative model by Smillie Ayoub (1975) and the deviation concept by Kjellen (1984a) connect the general systems theory to the sequencing and energy models of accident causation. They encompass technical, organizational and human components of the system. Various methods of system safety analysis (e.g. fault tree analysis, incidental factor analysis) support the identification of technical and human deviations as well as the analysis of the conditions and consequences of these deviations. From the discussion of near misses and conflicts it became clear that frameworks of accident causation should cover all kinds of incidents, thus becoming frameworks of incidents. 

One of the origins of this view of error and accident causation is the theory of accident proneness, which tried to show that a small number of individuals were responsible for the majority of accidents. Despite a number of studies that have shown that there is little statistical evidence for this idea (see, e.g., Shaw and Sichel, 1971) the belief remains, particularly in traditional industries, that a relatively small number of individuals accoimt for the majority of accidents. Another element in the emphasis on individual responsibility has been the legal dimension in many major accident investigations, which has often been concerned with attributing blame to individuals from the point of view of determining compensation, rather than in identifying the possible system causes of error. 

The somewhat controversial theory of risk homeostasis is relevant to a discussion of risk taking. RHT was developed initially in the area of driving behavior (Wilde, 1984). The theory states that accident rates are not determined by actual levels of intrinsic risk but by the levels of risk acceptable to individuals in the situation. The theory implies that people adjust their risk-taking behavior to maintain a constant level of perceived risk. Thus, if improved safety measures are introduced (e.g., better guarding, improved protection systems then individuals will behave in a more risky fashion in order to maintain their accustomed levels of risk. 

This book is divided into five parts the problem, accidents, health risk, hazard risk, and hazard risk analysis. Part 1, an introduction to HS AM, presents legal considerations, emergency planning, and emergency response. This Part basically ser es as an oveiwiew to the more teclmical topics covered in the remainder of the book. Part 11 treats the broad subject of accidents, discussing fires, explosions and other accidents. The chapters in Parts 111 and Part IV provide introductory material to health and hazard risk assessment, respectively. Pai1 V examines hazaid risk analysis in significant detail. The thiee chapters in this final part include material on fundamentals of applicable statistics theory, and the applications and calculations of risk analysis for real systems. 

Quite by accident Jennifer discovered that her tendon and connective tissue problems and chronic fatigue were exasperated by molds and chemical exposures. Her understanding is that her various health problems are related to but not completely caused by MCS. One doctor s theory is that her MCS and connective tissue problems may be caused by a metabolic dysfunction. Another doctor, after looking at her extensive medical history, told her she will never find an answer. Jennifer summarizes her ten years of medical tests and examinations by saying that her body doesn t absorb nutrients and her immune system has collapsed. 

I consider three sources of variation in behavior across societies. First, societies may exhibit different behaviors because for historical reasons they have ended up in different coordination equilibria. In theory, the United Kingdom and the United States could be identical in all respects except that people drive on the left in the first country and on the right in the second, together with features that flow directly from this difference. Differences in metric systems, number systems, and calendars can also generate differences in behavior that need not reflect anything but accidents of history. Second, behavioral differences may be due to different norms and values. I especially emphasize the importance of social norms in explaining cultural variation. Norms, in turn, are backed by... 

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