In 1990 James Reason introduced the world to the Swiss Cheese model of accident causation. This now forms the basis of most risk modelling.
In Reason’s representative framework each layer of cheese represents a barrier that can prevent an unacceptable event from occurring. Therefore, in theory, lapses and weaknesses in one defense do not allow a risk to materialize, since other defenses also exist, to prevent a single point of failure. However, each barrier also has flaws. If all of these ‘holes’ line up, as they sometimes will, then a catastrophic event can occur. There are two types of holes: latent conditions (existing problems) and active failures (acute problems leading to the accident).
The use of Reason’s model helps us to expose the multiple, smaller failures that can contribute to an event. It is far too easy just to blame human error, as so often happens. As Reason said: “We cannot change the human condition, but we can change the conditions under which humans work”. If lessons are to be learned from what happened then this larger context needs to be properly considered.
You can find out more about the model here: Click here. The Swiss cheese model is respected and considered to be a useful method of relating concepts. It has also been subject to criticism that it is used too broadly, and without enough other models or support. For those who wish to consider it more deeply, there are some thoughts on its practical application and potential fishhooks here: View Here.