Accident models

Lazaro, M. A. et al, 1997, Model Review and Evaluation for Application in DE Safety Basis Documentation of Chemical Accidents Modeling Guidance for Atmospheric Dispersion and Consequence Assessment, ANL/EAD/TM-75, September. 

Traditional accident models were devised to explain losses caused by failures of physical devices (chain or tree of failure events) in relatively simple systems. They are less useful for explaining accidents in software-intensive systems and for non-technical aspects of safety such as organizational culture and human decision-making. Creation of an infrastructure based on which safety analysis can function efficiently and effectively is needed. A so called safety culture for a development company and processes associated with routine tasks there, in general, is now identified as an area of root cause of accidents and that there is the greatest... 

And construction operatives do take risks, as evidenced in industry-specific accident models. For example, two of the three root causes of accidents under the construction industry-specific Accident Root Cause Tracing Model (ARCTM) developed by Abdelhamid and Everett (2000) are assigned to deliberate risk taking on the part of operatives. Whether they decided to proceed with work activities once an existing unsafe condition had been identified, or decided to act unsafely regardless of the initial conditions of the work environment, either approach requires the identification of the risk - and its subsequent acceptance on behalf of the workforce. 

Leveson, N. (2004). A new accident model for engineering safer systems. Scfety Science 42) 231-10. 

ABSTRACT In recent years, coal mine accident happened frequently in our country. Based on the statistics about coal mine accident and accident mechanism analysis, the paper find out the main reason that lead to coal mine accident happened frequently in our country. Based on the existing accident model, it put forward coal mine accident human error model. And make detailed factor analysis and effective analysis for the model. Then, from the angle of team, the paper put forward team safety management mode for coal mine enterprises and the corresponding safety control measures. It is a new safe management thought for China s coal mine industry. 

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... 

An underlying assumption of all accident models is that there are common patterns in accidents and that they are not simply random events. Accident models impose patterns on accidents and influence the factors considered in any safety analysis. Because the accident model influences what cause(s) is ascribed to an accident, the countermeasures taken to prevent future accidents, and the evaluation of the risk in operating a system, the power and features of the accident model used will greatly affect our ability to identify and control hazards and thus prevent accidents. 

The earliest formal accident models came from industrial safety (sometimes called occupational safety) and reflect the factors inherent in protecting workers from injury or illness. Later, these same models or variants of them were applied to the engineering and operation of complex technical and social systems. At the beginning, the focus in industrial accident prevention was on unsafe conditions, such as open blades and unprotected belts. While this emphasis on preventing unsafe conditions was very successful in reducing workplace injuries, the decrease naturally started to slow down as the most obvious hazards were eliminated. The emphasis... 

The most common accident models today explain accidents in terms of multiple events sequenced as a forward chain over time. The events included almost always involve some type of failure event or human error, or they are energy related (for example, an explosion). The chains may be branching (as in fault trees) or there may be multiple chains synchronized by time or common events. Lots of notations have been developed to represent the events in a graphical form, but the underlying model is the same. Figure 2.4 shows an example for the rupture of a pressurized tank. 

Effectively preventing accidents in complex systems requires using accident models that include that social system as well as the technology and its underlying science. Without understanding the purpose, goals, and decision criteria used to construct and operate systems, it is not possible to completely understand and most effectively prevent accidents. 

An accident model should encourage a broad view of accident mechanisms that expands the investigation beyond the proximate events A narrow focus on operator actions, physical component failures, and technology may lead to ignoring some of the most important factors in terms of preventing future accidents. The whole concept of root cause needs to be reconsidered. 

Event-based models work best for accidents where one or several components fail, leading to a system failure or hazard. Accident models and explanations involving only simple chains of failure events, however, can easily miss subtle and complex... 

The search for a new model, resulting in the accident model presented in part II, was driven by the following goals ... 

STAMP AN ACCIDENT MODEL BASED ON SYSTEMS THEORY... 

The STAMP (System-Theoretic Accident Model and Processes) accident model is based on these principles. Three basic constructs underlie STAMP safety constraints, hierarchical safety control structures, and process models. 

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. 

STAMP provides a direction to take in creating these new hazard analysis and prevention techniques. Because in a system accident model everything starts from constraints, the new approach focuses on identifying the constraints required to maintain safety identifying the flaws in the control structure that can lead to an accident (inadequate enforcement of the safety constraints) and then designing a control structure, physical system and operating conditions that enforces the constraints. 

Promoting a Just Culture requires getting away from blame and punishment as a solution to safety problems. One of the new assumptions in chapter 2 for an accident model and underlying STAMP was ... 

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. 

Ludwig Beimer, Jr. wrote this in the Conclusions to a study titled Rating Accident Models and Investigation Methodologies, which was... 

The number of conceptual accident models that drive government accident investigation programs seems unnecessarily diverse. Since they conflict, all models can not be valid [p. 124],... 

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