Whilst some models are helpful they are never accurate. Models are symbols/myths that convey a semiotic purpose but in themselves ought not to be considered absolute. This is why we find metaphors and symbols helpful, neither are scientific or accurate but serve as a guide that is interpreted. Such is the myth of the Hierarchy of Controls (HoC). It is just a reality of human language that we seek to clarify things by using something that it is not (metaphor). Try read Metaphors We Live By (Lakhoff and Johnson) or the Rule of Metaphor by Paul Ricoeur.
The idea of a Hierarchy is just that, it creates the idea of a rank order, that is why the model of the HoC uses the metaphor of up-down to demonstrate importance and power, down to the so called ‘least powerful’ link in the controls. Like any linear model Safety seems to get a hold of myths like HoC and turn them into an absolute truth, when it is not. At best the model should be called a ‘Selection of Controls’and even then it is amazingly deficient. The HoC model is entirely focused on physical barriers, it’s all about objects. Nothing in the HoC myth gives one a clue to any social, psychological or cognitive factors associated with risk.
BTW, in SPoR myth and symbols are understood as the same thing. The flip side of the same coin. In the Social Psychology of Risk (SPoR) one learns to understand things semiotically and knows that models, colours and shapes communicate to the unconscious and are often much more powerful than text. Here’s a simple test:
So when did you look left? Probably after you first looked right. In semiotics we learn that images, models, shares, graphics, models and symbols have much more power than text. If you want to learn more about semiotics you can do the online module here: https://cllr.com.au/product/semoiotics-and-the-social-psychology-of-risk-unit-3/
So back to the HoC myth. Do a search for any HoC model and of course it falls for the favourite safety shape, the pyramid/triangle. Ah, doesn’t Safety love triangles and pyramids (https://safetyrisk.net/nonsense-curves-and-pyramids/ ).
So not only does the HOC model get portrayed as a HIERARCHY but this is reinforced with the psychology of colour and shape. So, combining all semiotic cues of shape, colour and order the HIERARCHY of controls gives the idea of rank order when there is none.
In SPoR we recommend a much broader and less hierarchical approach to tackling risk. It is a model that better understands the motivations and context of decision making and better matches response with context. See Figure 1. Selection of Controls.
Figure 1. Selection of Controls.
In the Selection of Controls Model much greater emphasis is placed upon the skills of the observer and the adaptability of response. For those who are familiar with the Workspace, Headspace, Groupspace model in SPoR there is an understanding that life is much more messy and disorderly than a hierarchy. The circular model doesn’t get drawn into the hierarchy/pyramidic myth but allows for one to see a much more interconnected way of tackling risk through an interconnectedness of factors and an interconnectedness of responses.
Like all models, it is not intended to be perfect but does attempt to help people get away from this linear mechanical myth that views controls are hierarchical and orderly.
Where I do find the HoC model to be useful is in plant and process design. While all you said about it above is true, once the focus is on the physical, the model becomes useful (not all-encompassing and not perfect, but a good way to describe certain aspects). If you have to design a plant and need to determine if you will need a barrier, an alarm or both, this “hierarchy” has its uses. However, it has been abused and misused in areas where it became completely irrelevant. (Obviously, we are now in the domain of engineering, and not “Safety”.)
But, even then, how does it encourage you to think about the unintended impacts on other parts of the process, let alone how will humans interact with or be impacted by that control?
Rob Long says
The real problem for me is what is created by the idea of a hierarchy, more linear in-line model as if risk and events are linear and hierarchical. It is also a problem of how this model and many other safety models has been made a norm in the industry. All models seek to explain something but they are only models that represent something else, they are not the thing in itself. The real challenge is how much the model is helpful in tackling risk.
and even the semiotics of the shape prime PPE and the most common, foundational control. Surely most humans would do the best they could with what they had or knew and dont need some silly pyramid to remind them of a process they should follow
casey senecal says
Agree, this model would promote the idea that more than one control needs to be applied. Would encourage more thought regarding suitable measures.
SPoR Social Psychology of Risk – something i have now learnt and will take away; thanks Rob!
Love the myth debunking and it makes sense. In safety we often apply a poor mindset that is shaped from regulation, compliance, company fear of prosecution, norms, popular beliefs and those at the top not knowing what to do, even worse, being scared to do something differently in fear of being lambasted if it goes wrong. I’ll be sure to read more from yourself,
Rob Long says
Rob long says
Thanks Brian, makes much more sense than a hierarchy.
Hi Rob, I like the model you have shown above related to selection of controls. Clear how everything fits together and none more important than the other depending on the situation. Cheers Brian