Randy Chandler
The Swiss cheese model of accident causation is a model used in risk analysis and risk management. It was originally proposed by James Reason of the University of Manchester. The model likens human system defences to slices of Swiss cheese with holes, representing weaknesses in individual parts of the system. The holes vary in size and position across the slices. When the holes align, a failure occurs, leading to an accident. The Swiss cheese model has been widely accepted and applied in various fields, including aviation, engineering, healthcare, and emergency services. It helps organisations understand why accidents occur despite their efforts to prevent them and develop strategies to improve safety. However, some critics argue that it oversimplifies the complexity of human error.
| Characteristics | Values |
|---|---|
| Creator | James Reason |
| Other Names | Cumulative Act Effect, Multi-Layer Defence Model |
| Use Cases | Risk analysis, risk management, process safety, accident investigation, patient safety, safety incident causation |
| Visualization | Multiple layers of Swiss cheese with holes of varying sizes and positions |
| Holes | Represent potential failure points or weaknesses in the system |
| Slices of Cheese | Represent barriers or lines of defence against accidents |
| Alignment of Holes | Enables a "trajectory of accident opportunity" leading to system failure |
| Active Failures | Unsafe acts directly linked to an accident, e.g. human error |
| Latent Failures | Underlying causes or conditions that trigger active failures |
| Applications | Aviation, engineering, healthcare, emergency services, cybersecurity, firefighting |
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What You'll Learn
Human errors are only one layer of safety defences
The Swiss Cheese model of accident causation, originally proposed by James Reason, likens human system defences to multiple slices of Swiss cheese, stacked side by side, with gaps in between each slice. The holes in the cheese slices represent individual weaknesses in different parts of the system, and they vary in size and position across the slices.
Reason's model recognises that people working in complex systems make errors or violate procedures for reasons beyond individual psychology. For example, poor design, gaps in supervision, manufacturing defects, clumsy automation, and inadequate tools may be present for years before they combine with local circumstances and human errors to penetrate the system's defences. Therefore, workers are not to blame, as it is the latent conditions that fail to protect workers and lead to incidents.
The Swiss Cheese model is widely used within process safety, especially in oil and gas drilling and production, and in the engineering of firefighting systems. It is also applied in healthcare, where it has become the dominant paradigm for analysing medical errors and patient safety incidents.
Overall, the Swiss Cheese model is a powerful approach to accident investigation and prevention, helping organisations understand why accidents occur despite their best efforts to prevent them.
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Holes in the cheese represent failure or absence of safety barriers
The Swiss Cheese Model of accident causation, originally proposed by James Reason, is a model used in risk analysis and risk management. It is a widely accepted model, particularly in patient safety circles and healthcare quality improvement.
The model likens an organisation's defences against failure to a series of slices of Swiss cheese, with holes in the cheese slices representing individual weaknesses in the system. These holes are referred to as "eyes" and symbolise the failure or absence of safety barriers.
Each slice of cheese is seen as a line of defence against accidents, with each slice having its own unique set of holes. These holes represent areas of potential failure or shortcomings. The holes vary in size and position across the slices, indicating that weaknesses in the system are not always predictable or static; they emerge and disappear with changing safety issues.
When the holes in the cheese slices align, it creates a "trajectory of accident opportunity", allowing a hazard to pass through all the defences and leading to a failure. This illustrates that accidents typically result from a combination of factors, including latent errors and active errors, rather than a single root cause. Latent errors are inherent weaknesses in a procedure, machine, or system, while active errors are unsafe behaviours carried out by individuals.
The Swiss Cheese Model helps organisations understand why accidents occur despite their best efforts to prevent them. It is a useful tool for identifying weak points and developing strategies to address them.
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The model is widely used within process safety
The Swiss Cheese Model of accident causation is a model used in risk analysis and risk management. It is based on the idea that an organisation's defences against failure can be modelled as a series of barriers, represented as slices of Swiss cheese with holes of varying sizes and positions. These holes represent weaknesses or potential failure points in the system, and when they align, a failure occurs. This model has gained widespread acceptance and is now commonly used within process safety.
Within process safety, the Swiss Cheese Model is applied to identify and mitigate risks in various industries, including oil and gas drilling and production. Each slice of cheese in the model represents a safety-critical system, and the holes in the cheese symbolise the potential failures or weaknesses within that system. By identifying and addressing these weaknesses, organisations can improve their overall defence against risks.
The model is also used to investigate accidents and incidents after they have occurred. By analysing the alignment of holes (weaknesses) in the cheese slices, organisations can identify where defences against failure broke down and develop strategies to prevent similar incidents in the future. This approach helps organisations learn from their mistakes and continuously improve their safety measures.
In addition, the Swiss Cheese Model is valuable for understanding the complex interplay between human error and systemic failures. It recognises that fallibility is an inherent part of the human condition and that errors or violations of procedures can occur due to various factors beyond individual control. By considering both human factors and systemic issues, organisations can develop more comprehensive safety measures and interventions.
The Swiss Cheese Model has been applied in healthcare, engineering, aviation, and emergency services to enhance safety and reduce accidents. However, some critics argue that the model may oversimplify the complexity of human error, particularly in healthcare settings. Despite this criticism, the model remains widely accepted and utilised by patient safety professionals to analyse medical errors and patient safety incidents.
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The model is used to understand why accidents occur
The Swiss Cheese Model is a model of accident causation that is used to understand why accidents occur. It was originally proposed by James Reason of the University of Manchester. The model is used in risk analysis and risk management and has gained widespread acceptance, especially in patient safety circles.
The model likens an organisation's defences against failure to a series of slices of Swiss cheese, with holes representing weaknesses in individual parts of the system. These holes are continually varying in size and position across the slices. When the holes in all the slices align, it creates a "trajectory of accident opportunity", allowing a hazard to pass through all the defences and leading to a failure. This illustrates how failures usually result from a combination of factors rather than a single root cause.
In the model, each slice of cheese represents a line of defence against accidents, such as management, allocation of resources, or a safety program. The holes in the cheese depict the failure or absence of safety barriers within a system. For example, in a healthcare context, a hole could be a nurse mis-programming an infusion pump or a resident not providing an adequate briefing during a patient handoff.
The Swiss Cheese Model helps organisations identify weak points and develop strategies to address them. It also highlights that fallibility is an inherent part of the human condition, and that errors or violations of procedures occur for reasons beyond individual psychology. By understanding the model, organisations can improve their safety defences and prevent incidents from occurring.
The model has been applied in various fields, including aviation safety, engineering, healthcare, emergency services, and computer security. However, some critics argue that it oversimplifies the complexity of human error and accident occurrence. Despite this, the Swiss Cheese Model remains a powerful tool for accident investigation and prevention, providing valuable insights into the causes of accidents and failures.
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The model is used to identify weak points and develop strategies
The Swiss Cheese Model is widely used within process safety and risk management. It is used to identify weak points and develop strategies to prevent accidents and failures.
In the model, each slice of cheese represents a safety-critical system or a line of defence against accidents. These slices are not solid; they are full of holes, which represent weaknesses or potential failure points in the system. These holes are not static; they are continually varying in size and position across the slices. When the holes in each slice align, a failure occurs, and an accident can take place.
The model is useful for identifying weak points because it shows how accidents are usually caused by a combination of factors, rather than a single root cause. This combination of factors includes latent errors, which are inherent in a procedure, machine, or system, and active errors, which are unsafe behaviours carried out by individuals. Latent errors are triggered by active errors, and together, they create a "trajectory of accident opportunity".
By understanding the Swiss Cheese Model, organisations can develop strategies to combat accidents. This may involve inserting additional layers of cheese into the system, as in the case of Lubnau, Lubnau II, and Okray's application of the model to the engineering of firefighting systems. Alternatively, organisations can work to identify and address weaknesses in their safety defences before an incident occurs. This could include improving training, tools, and equipment, or addressing issues with supervision, procedures, or automation.
The model has been particularly useful in industries such as aviation, engineering, healthcare, and emergency services. However, some critics argue that it oversimplifies the complexity of human error and accident causation.
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Frequently asked questions
The Swiss Cheese Model is a theory of accident causation that likens human system defences to slices of Swiss cheese with holes representing weaknesses in the system. When the holes align, a failure occurs.
The holes in the cheese represent individual weaknesses or shortcomings in the system. These are also referred to as latent errors or active errors. Latent errors are built into procedures, systems, or machines, while active errors are unsafe behaviours carried out by individuals.
Each slice of cheese represents a line of defence or barrier against accidents. In an organisation, these slices can include management, allocation of resources, and safety programs.
A latent error could be a faulty fire alarm system. An active error could be an employee choosing not to follow safety procedures, such as cleaning flammable debris from a machine. When combined, these errors could result in a serious fire accident.
By identifying latent and active errors, organisations can develop strategies to prevent accidents. This may include implementing additional safety measures, such as regular safety training for employees, to address potential weaknesses in the system.
