Accident Analysis As Well As Systems Thinking

Complex socio-technical systems fail; that is, accidents occur. And it is enormously of import for engineers as well as policy makers t...

Complex socio-technical systems fail; that is, accidents occur. And it is enormously of import for engineers as well as policy makers to accept a ameliorate means of thinking nigh accidents than is the electrical current protocol next an air crash, a chemic industrial plant life fire, or the reveal of a contaminated drug. We demand to empathise ameliorate what the systems as well as organizational causes of an accident are; fifty-fifty to a greater extent than importantly, nosotros demand to accept a reason for improving the prophylactic functioning of complex socio-technical systems past times identifying ameliorate processes as well as ameliorate alarm indicators of impending failure.

Influenza A virus subtype H5N1 long-term leader inwards the land of systems-safety thinking is Nancy Leveson, a professor of aeronautics as well as astronautics at MIT as well as the writer of Safeware: System Safety as well as Computers (1995) as well as Engineering a Safer World: Systems Thinking Applied to Safety (2012). Leveson has been a detail advocate for 2 insights: looking at security equally a systems characteristic, as well as looking for the organizational as well as social components of security as well as accidents likewise equally the technical lawsuit histories that are to a greater extent than ofttimes the focus of accident analysis. Her approach to security as well as accidents involves looking at a engineering scheme inwards price of the laid upward of controls as well as constraints that accept been designed into the procedure to preclude accidents. "Accidents are seen equally resulting from inadequate command or enforcement of constraints on safety-related demeanor at each aeroplane of the scheme evolution as well as scheme operations command structures." (25)

The abstract for her essay "A New Accident Model for Engineering Safety" (link) captures both points.

New engineering is making key changes inwards the etiology of accidents as well as is creating a demand for changes inwards the explanatory mechanisms used. We demand ameliorate as well as less subjective agreement of why accidents occur as well as how to preclude hereafter ones. The most effective models volition acquire beyond assigning blame as well as instead assistance engineers to acquire equally much equally possible nigh all the factors involved, including those related to social as well as organizational structures. This newspaper presents a novel accident model founded on basic systems theory concepts. The usage of such a model provides a theoretical foundation for the introduction of unique novel types of accident analysis, endangerment analysis, accident prevention strategies including novel approaches to designing for safety, take away chances assessment techniques, as well as approaches to designing performance monitoring as well as security metrics.

The accident model she describes inwards this article as well as elsewhere is STAMP (Systems-Theoretic Accident Model as well as Processes). Here is a brusk description of the approach.

In STAMP, systems are viewed equally interrelated components that are kept inwards a state of dynamic equilibrium past times feedback loops of data as well as control. Influenza A virus subtype H5N1 scheme inwards this conceptualization is non a static design—it is a dynamic procedure that is continually adapting to attain its ends as well as to react to changes inwards itself as well as its environment. The master copy blueprint must non exclusively enforce appropriate constraints on demeanor to ensure prophylactic operation, but the scheme must move along to operate safely equally changes occur. The procedure leading upward to an accident (loss event) tin last described inwards price of an adaptive feedback business office that fails to hold security equally performance changes over fourth dimension to run into a complex laid upward of goals as well as values.... The basic concepts inwards STAMP are constraints, command loops as well as procedure models, as well as levels of control. (12)

The other quest of emphasis inwards Leveson's handling of security is her consistent endeavour to include the social as well as organizational forms of command that are a component of the prophylactic functioning of a complex technological system.

Event-based models are wretched at representing systemic accident factors such equally structural deficiencies inwards the organization, administration deficiencies, as well as flaws inwards the security civilisation of the companionship or industry. An accident model should encourage a wide persuasion of accident mechanisms that expands the investigation from beyond the proximate events. (6)

She treats the organizational backdrop of the engineering procedure inwards query equally existence a crucial element of the prophylactic functioning of the process.

Social as well as organizational factors, such equally structural deficiencies inwards the organization, flaws inwards the security culture, as well as inadequate administration determination making as well as command are straight represented inwards the model as well as treated equally complex processes rather than merely modeling their reflection inwards an lawsuit chain. (26)

And she treats organizational features equally to a greater extent than or less other shape of command scheme (along the lines of Jay Forrester's early on definitions of systems inwards Industrial Dynamics.

Modeling complex organizations or industries using scheme theory involves dividing them into hierarchical levels amongst command processes operating at the interfaces betwixt levels (Rasmussen, 1997). Figure iv shows a generic socio-technical command model. Each system, of course, must last modeled to reverberate its specific features, but all volition accept a construction that is a variant on this one. (17)

Here is figure 4:

The approach embodied inwards the STAMP framework is that security is a systems effect, dynamically influenced past times the command systems embodied inwards the full procedure inwards question.

In STAMP, systems are viewed equally interrelated components that are kept inwards a state of dynamic equilibrium past times feedback loops of data as well as control. Influenza A virus subtype H5N1 scheme inwards this conceptualization is non a static design—it is a dynamic procedure that is continually adapting to attain its ends as well as to react to changes inwards itself as well as its environment. The master copy blueprint must non exclusively enforce appropriate constraints on demeanor to ensure prophylactic operation, but the scheme must move along to operate safely equally changes occur. The procedure leading upward to an accident (loss event) tin last described inwards price of an adaptive feedback business office that fails to hold security equally performance changes over fourth dimension to run into a complex laid upward of goals as well as values. (12) 

And:

In systems theory, systems are viewed equally hierarchical structures where each aeroplane imposes constraints on the activity of the aeroplane beneath it—that is, constraints or lack of constraints at a higher aeroplane permit or command lower-level demeanor (Checkland, 1981). Control laws are constraints on the relationships betwixt the values of scheme variables. Safety-related command laws or constraints thus specify those relationships betwixt scheme variables that constitute the nonhazardous scheme states, for example, the ability must never last on when the access door is open. The command processes (including the physical design) that enforce these constraints volition trammel scheme demeanor to prophylactic changes as well as adaptations. (17)

Leveson's agreement of systems theory brings along amongst it a rigid project design of "emergence". She argues that higher levels of systems receive properties that cannot last reduced to the properties of the components, as well as that security is i such property:

In systems theory, complex systems are modeled equally a hierarchy of levels of organization, each to a greater extent than complex than the i below, where a aeroplane is characterized past times having emergent or irreducible properties. Hierarchy theory deals amongst the key differences betwixt i aeroplane of complexity as well as another. Its ultimate aim is to explicate the relationships betwixt unlike levels: what generates the levels, what separates them, as well as what links them. Emergent properties associated amongst a laid upward of components at i aeroplane inwards a hierarchy are related to constraints upon the aeroplane of liberty of those components. (11)

But her agreement of "irreducible" seems to last unlike from that usually used inwards the philosophy of science. She does inwards fact believe that these higher-level properties tin last explained past times the scheme of properties at the lower levels -- for example, inwards this passage she asks "... what generates the levels" as well as how the emergent properties are "related to constraints" imposed on the lower levels. In other words, her seat seems to last similar to that advanced past times Dave Elder-Vass (link): emergent properties are properties at a higher aeroplane that are non possessed past times the components, but which depend upon the interactions as well as composition of the lower-level components.

The domain of security engineering scientific discipline as well as accident analysis seems similar a especially suitable house for Bayesian analysis. It seems unavoidable that accident analysis involves both frequency-based probabilities (e.g. the frequency of heart failure) as well as expert-based estimates of the likelihood of a detail sort of failure (e.g. the likelihood that a develop operator volition slacken attending to rail warnings inwards answer to companionship pressure level on timetable). Bayesian techniques are suitable for the chore of combining these diverse kinds of estimates of take away chances into a unified calculation.

The topic of security as well as accidents is especially relevant to because it expresses really clearly the causal complexity of the social the world inwards which nosotros live. And rather than merely ignoring that complexity, the systematic written report of accidents gives us an avenue for arriving at ameliorate ways of representing, modeling, as well as intervening inwards parts of that complex world.