Reasons Organisational Model of System Accidents

Posted by Andrew McGiffert |06 Feb 13 | 0 comments

Reason proposed that there are two types of accidents, those that happen to individuals and those that happen to organisations, (Reason, 1997, 1). Although individual accidents are much more common Reasons model focuses on organizational accidents. This model can be used to explain accident causation in complex technological systems, such as nuclear power plants, commercial aviation, rail transport, etc.

Organisational accidents do not occur due to a single human error; they have multiple causes involving many people operating at different levels. In comparison, individual accidents are usually caused by a specific person or group ‘which is often both the agent and the victim of the accident’, (Reason, 1997, 1).

Reason (1997, 1) defines organization accidents as “situations in which latent conditions (arising from such aspects as management decision practices, or cultural influences) combine adversely with local triggering events (such as weather, location, etc.) and with active failures (errors and/or procedural violation) committed by individuals or teams at the sharp end of an organization, to produce the accident”.

Defences, barriers and safeguards are key requirements in complex safety systems. Reason (1997, 9) proposes that accidents emerge due to holes in barriers and safeguards. The dynamics of accident causation are illustrated in the ‘Swiss Cheese Model of Defences’. 


 In a perfect system defensive layers should not contain any holes, thus preventing a hazard from ‘getting through’ and causing an accident. Over time defences break down, as organizational goals change and as people become complacent holes begin to appear in the defensive layers, increasing the likelihood for a hazard to ‘get through’. Holes within one layer will not necessarily cause an accident; however when holes in multiple layers line up the likelihood of an accident occurring increases, bringing hazards into damaging contract with victims. Holes in defences arise for two reasons: active failures and latent conditions (Reason, 1997, 10). Previously latent conditions were known as latent errors and then latent failures (Reason, 1990, 173). The term latent conditions was adopted in Reasons new text (1997), as he explained that latent conditions do not necessarily involve either error or failure.

It is now recognized and accepted that mistakes do happen; it is a part of the human condition that people will occasionally make errors or violate procedures, the reasons for these lapses usually go beyond the individual and are a result of their environment and other factors, these reasons are latent conditions, (Reason, 1997, 10).

Latent conditions include things like “poor design, gaps in supervision, undetected manufacturing defects or maintenance failures, unworkable procedures, clumsy automation, shortfalls in training, less than adequate tools and equipment” (Reason, 1997, 10). These latent conditions may be present within the workplace for some-time and it is not until they are combined with ‘local circumstances’ and ‘active failures’ that they begin to penetrate the systems layers of defences (Reason, 1997, 10).

Active failures are the unsafe acts committed by people who are in direct contact with the system; for example, slips, trips, mistakes are all active failures. The effect of active failures are usually felt immediately and have a brief impact on the integrity of the defences (Reason, 1990, 173). Unsafe Acts in many cases are now commonly viewed as consequences rather than principal causes (D Woods et al., 1994). This theory differs from the Domino model, where the emphasis of the accident is placed on the ‘middle of the sequence’ being the unsafe act or ‘active failure’, (Heinrich and Granniss, 1959, 4). This could be considered an advantage of Reasons model, providing for further analysis of the environmental factors and prompting for greater controls, rather than controlling individuals.

The example provided previously in the Domino model post has been analysed below using Reasons model of Active Failures and Latent Conditions.

Active Failures

Latent Conditions

Supervisor did not inform the worker earlier of the impending pick up.

Gloves were located in a storage bin under a desk out of easy reach.

Supervisor did not understand the required physical level of work involved in moving the items.

Competency assessment against working practices did not take place. No training records for the employee existed.

Employee did not use provided riggers gloves.

Working practices were not clearly displayed in the work area.

Employee did not object to performing the task.

Receiving area was short staffed.

Within my experiences, senior managers often want the attention of a failure and the surprise of the accident to simply go away, not wanting to accept that a change in beliefs, views and spending is needed. The easiest way for an organization to avoid accepting a need for change is to see the cause of the failure as something ‘local’, caused by one or more individuals who have behaved in an uncharacteristic way. (Dekker, S. 2006, 62).

“Failures can only be understood by looking at the whole system in which they took place. But in our reactions to failure, we often focus on the sharp end, where people were closest to causing or potentially preventing the mishap”, (Dekker, S. 2006, 60).

Using Reasons model of analysing active failures and latent conditions it is not possible to simply blame the worker, the unsafe act, or failure.

Analysing the latent conditions in the example it becomes apparent that the failures are by-products of the latent conditions, holes in the defences which have allowed the failures to occur, or contributed to their circumstances. It is clear that there is a larger organizational problem, a lack of awareness and safety culture – which through the holes left by a range of active conditions and active failures has allowed an accident to occur causing injury to an employee. I did not make this same finding when using the domino sequence.

The advantage of using this model in the workplace is that it can provide a greater understanding as to why an incident has occurred, rather than assigning blame Reasons model identifies the circumstances which have led to the occurrence enabling risk controls to be applied to the active failures, and prompting for the development of strategies and action plans to reduce latent conditions.

This may be seen as a disadvantage by some, particularly in organisations where they do not want to identify their processes and controls as causation factors and would rather assign blame to an individual or group of workers.


Dekker, S. 2006. The Field Guide to Understanding Human Error. England: Ashgate Publishing Limited.

Heinrich, H.W., and E.R. Granniss. 1959. Industrial Accident Prevention. United States of America: McGraw-Hill Book Company Inc.

Reason, J. 1990. Human Error. United States of America: Cambridge University Press.

Reason J. 1997. Managing the Risks of Organisational Accidents. England: Ashgate Publishing Limited.

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