In the Swiss Cheese model, individual weaknesses are modelled as holes in slices of swiss cheese, such as this Emmental. They represent the imperfections in individual safeguards or defences, which in the real world rarely approach the ideal of being completely proof against failure.

The Swiss Cheese model of accident causation is a model used in the risk analysis and risk management of human systems. It likens human systems to multiple slices of swiss cheese, stacked together, side by side. It was originally propounded by British psychologist James T. Reason in 1990, and has since gained widespread acceptance and use in healthcare, in the aviation safety industry, and in emergency service organizations. It is sometimes called the cumulative act effect. Download high resolution version (948x800, 86 KB)This is a file from the Wikimedia Commons, a repository of free content hosted by the Wikimedia Foundation. ... Download high resolution version (948x800, 86 KB)This is a file from the Wikimedia Commons, a repository of free content hosted by the Wikimedia Foundation. ... Country of origin Switzerland Region, town Berne, Emme Source of milk Cows Pasteurized Traditionally, no Texture semi-hard Aging time 3-12 months depending on variety Certification No Emmental, Emmentaler, Emmenthal, or Emmental cheese is a Swiss cheese. ... Risk analysis is a technique to identify and assess factors that may jeopardize the success of a project or achieving a goal. ... Risk management is the process of measuring, or assessing, risk and developing strategies to manage it. ... Cubes of Swiss cheese This article is about a variety of cheese known as Swiss cheese in some areas. ... Air safety is a broad term encompassing the theory, investigation and categorization of flight failures, and the prevention of such failures through appropriate regulation, as well as through education and training. ...

Reason hypothesizes that most accidents can be traced to one or more of four levels of failure: Organizational influences, unsafe supervision, preconditions for unsafe acts, and the unsafe acts themselves. In the Swiss Cheese model, an organization's defences against failure are modelled as a series of barriers, represented as slices of swiss cheese. The holes in the cheese slices represent individual weaknesses in individual parts of the system, and are continually varying in size and position in all slices. The system as a whole produces failures when all of the holes in each of the slices momentarily align, permitting (in Reason's words) "a trajectory of accident opportunity", so that a hazard passes through all of the holes in all of the defenses, leading to a failure.^[1][2][3]

Frosch^[4] describes Reason's model in mathematical terms as a being a model in percolation theory, which he analyses as a Bethe lattice. In mathematics, percolation theory describes the behavior of connected clusters in a random graph. ...

The Swiss Cheese model includes, in the causal sequence of human failures that leads to an accident or an error, both active failures and latent failures. The former concept of active failures encompasses the unsafe acts that can be directly linked to an accident, such as (in the case of aircraft accidents) pilot errors. The latter concept of latent failures is particularly useful in the process of aircraft accident investigation, since it encourages the study of contributory factors in the system that may have lain dormant for a long time (days, weeks, or months) until they finally contributed to the accident. Latent failures span the first three levels of failure in Reason's model. Preconditions for unsafe acts include fatigued air crew or improper communications practices. Unsafe supervision encompasses such things as, for example, two inexperienced pilots being paired together and sent on a flight into known adverse weather at night. Organizational influences encompass such things as reduction in expenditure on pilot training in times of financial austerity.^[5] Pilot error is a term used to describe the cause of a crash of an airworthy aircraft where the pilot is considered to be principally or partially at fault. ...

The same analyses and models apply in the field of healthcare, and many researchers have provided descriptive summaries, anecdotes, and analyses of Reason's work in the field. For example, a latent failure could be the similar packaging of two different prescription drugs that are then stored close to each other in a pharmacy. Such a failure would be a contributory factor in the administration of the wrong drug to a patient. Such research has lead to the realization that medical error can be the result of "system flaws, not character flaws", and that individual greed, ignorance, malice, or laziness are not the only causes of error.^[6] This article needs to be cleaned up to conform to a higher standard of quality. ...

Lubnau, Lubnau, and Okray^[7] apply Reason's Swiss Cheese model to the engineering of human systems in the field of firefighting, with the aim of reducing human errors by "inserting additional layers of cheese into the system", namely the techniques of Crew Resource Management. Crew (or Cockpit) Resource Management (CRM) training originated from a NASA workshop in 1979 that focused on improving air safety. ...

References

1. ^ Daryl Raymond Smith, David Frazier, L W Reithmaier, and James C Miller (2001). Controlling Pilot Error. McGraw-Hill Professional, 10. ISBN 0071373187. 
2. ^ Jo. H. Wilson, Andrew Symon, Josephine Williams, and John Tingle (2002). Clinical Risk Management in Midwifery: the right to a perfect baby?. Elsevier Health Sciences, 4–6. ISBN 0750628510. 
3. ^ Tim Amos and Peter Snowden (2005). “Risk managament”, Adrian J. B. James, Tim Kendall, and Adrian Worrall: Clinical Governance in Mental Health and Learning Disability Services: A Practical Guide. Gaskell, 176. ISBN 1904671128. 
4. ^ Robert A. Frosch (2006). “Notes toward a theory of the management of vulnerability”, Philip E Auerswald, Lewis M Branscomb, Todd M La Porte, and Erwann Michel-Kerjan: Seeds of Disaster, Roots of Response: How Private Action Can Reduce Public Vulnerability. Cambridge University Press, 88. ISBN 0521857961. 
5. ^ Douglas A. Wiegmann and Scott A. Shappell (2003). A Human Error Approach to Aviation Accident Analysis: The Human Factors Analysis and Classification System. Ashgate Publishing, Ltd., 48–49. ISBN 0754618730. 
6. ^ Patricia Hinton-Walker, Gaya Carlton, Lela Holden, and Patricia W. Stone (2006-06-30). “The intersection of patient safety and nursing research”, Joyce J. Fitzpatrick and Patricia Hinton-Walker: Annual Review of Nursing Research Volume 24: Focus on Patient Safety. Springer Publishing, 8–9. ISBN 0826141366. 
7. ^ Thomas Lubnau II, Randy Okray, and Thomas Lubnau (2004). Crew Resource Management for the Fire Service. PennWell Books, 20–21. ISBN 1593700067. 

For the Manfred Mann album, see 2006 (album). ... June 30 is the 181st day of the year (182nd in leap years) in the Gregorian Calendar, with 184 days remaining. ...

Further reading

• James Reason (2000-03-18). "Human error: models and management". British Medical Journal 320 (7237): 768–770. DOI:10.1136/bmj.320.7237.768. 
• James Reason (1990-10-26). Human Error. Cambridge University Press. ISBN 0521314194. 
• James Reason (1997). Managing the risks of organizational accidents. Aldershot: Ashgate. ISBN 1840141042. 
• James Reason (1995). "A System Approach to Organizational Error". Ergonomics 38: 1708–1721. 
• Carol Bayley (2004). “What medical errors can tell us about management mistakes”, Paul B. Hofmann and Frankie Perry: Management Mistakes in Healthcare: Identification, Correction, and Prevention. Cambridge University Press, 74–75. ISBN 0521829003. 
• Ron Westrum and Anthony J. Adamski (1998). Organizational factors associated with safety and mission success in aviation environments. Lawrence Erlbaum Associates, 84. ISBN 0805816801.  — Westrum and Adamski relate Reason's Swiss Cheese model to Westrum's "human envelope" model, where "around every complex operation there is a human envelope that develops, operates, maintains, interfaces, and evaluates the function of the sociotechnological system" and where the system "depends on the integrity of this envelope, on its thickness and strength". Westrum models latent failures as voids within this envelope, and active failures as factors external to the envelope that are acting to breach it.
• Scott A. Shappell and Douglas A. Wiegmann (February 2000). The Human Factors Analysis and Classification System—HFACS: The "Swiss cheese" model of accident causation. National Technical Information Service.
• John R. Horn and Philip D. Hansten. "Sources of Error in Drug Interactions: The Swiss Cheese Model", Pharmacy Times, 2005.
• Thomas V Perneger (2005-11-09). "The Swiss cheese model of safety incidents: are there holes in the metaphor?". BMC Health Services Research 5 (71). DOI:10.1186/1472-6963-5-71. 
• Young, M.S.; Shorrock, S.T.; and Faulkner, J.P.E (2005-06-14). Seeking and finding organisational accident causes: Comments on the Swiss cheese model. Department of Aviation, University of New South Wales. (also available on-line here) — a reminder that while Reason's model extends causation to latent failures, this is not at the expense of eliminating active failure entirely
• John J. Nance. "Just How Secure Is Airline Security?: The Swiss Cheese Model and What We've Really Accomplished Since 9/11", ABC News, 2005-04-12.
• James T. Luxhøj and Kimberlee Kauffeld (2003). "Evaluating the Effect of Technology Insertion into the National Airspace System". The Rutgers Scholar 3. 
• Elizabeth A. Howell and Mark R. Chassin (May 2006). Right? Left? Neither!. Morbidity & Mortality Rounds on the Web. Agency for Healthcare Research and Quality. — the application of the Swiss Cheese model to a specific case of medical error

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See also

• Systems engineering
• Root cause analysis