The Swiss cheese model of risk management
Do the holes line up?26th Mar 2021
Whatever your field, whether you are project managing a multibillion-rand development, overseeing the security on a small estate, getting the kids to school on time, or running a large hospital, you need to manage risk, minimise accidents, and ensure the smooth flow of a number of related tasks. We all have different ways of ensuring that this happens, but one brilliant model is as simple as a slice of cheese – or, more accurately, a lot of slices of cheese.
Of mice and cheese
As Robbie Burns so poetically puts it: ‘The best-laid plans of mice (and humans) go oft awry’*, which could lead to disaster. And one of the best ways to ensure that they don’t is through the use of cheese. But not just any old cheese – it’s got to be a good Emmentaler, Maasdam or Jarlsberg. The reason that only these cheeses work is that they are what people in the USA refer to as Swiss cheese, and that’s the cheese that James Reason used as his analogy for the Swiss cheese model, also called the cumulative act effect.
The original Swiss cheese is Emmentaler, crafted in the Valley of the Emme River (Emmental) in Switzerland, where it’s been made for nearly 1,000 years. At first, the cheesemakers were distressed at the big holes that formed in the cheese while it was fermenting and maturing, thinking they were defects, but they came to be regarded as a positive feature of what is undoubtedly one of the more delicious cheeses around. (And that’s saying a lot, because there are hundreds, if not thousands, of delicious cheeses.) This style of cheese is made in many parts of the world – in the Netherlands, it’s called Maasdam; in Norway, Jarlsberg; and, in the USA, Swiss cheese, or just ‘Swiss’. But we digress. Swiss cheese is characterised by its distinctive holes, which is why Reason used it for his analogy.
The Swiss cheese model
While analysing accidents and catastrophes, Reason – professor emeritus of psychology at the University of Manchester – realised that, for every big disaster, there were a number of small, cumulative causes – hazards – most of which were associated with human error. From there it was no great leap to work out that, if one or more of those hazards could have been eliminated or mitigated, the risk would have been decreased, and the disaster might have been averted.
He then worked on the assumption that risk was managed by inserting a number of barriers to hazards – checkpoints that would prevent accidents or incidents leading to system failure. If we think of these barriers as cheese, a slice of Gouda would be a perfect barrier, but perfect barriers do not exist in nature or in business. Barriers have holes in them, just like Swiss cheese.
There’s really nothing new about this model, it’s just a brilliant way of explaining something that all good managers know intuitively, but sometimes have difficulty communicating to their staff, their board, their members and other stakeholders.
Think of – say – the security system of an estate. There is a perimeter fence. Perfect. No bad people can get through. Right?
The perimeter fence is a good idea – more than a good idea – it’s essential. But it is not foolproof. It’s not Gouda, it’s Jarlsberg or Emmentaler. Which is why almost every estate also has CCTV cameras, and security patrols, and alarmed beams, and a host of other security elements.
In Reason’s Swiss cheese model, each of these elements can be thought of as a slice of yummy Emmentaler. It’s good, but it’s not perfect. (As a cheese, Emmentaler is perfect, and it’s perfect as an analogy, but only because it so perfectly illustrates the imperfection of reality.)
So the fence is one slice of Swiss cheese, with holes. The CCTV cameras are another slice, the security patrols another slice, and on we go – each slice with its own particular pattern of holes.
Lining up the holes
So if, for example, I wanted to sneak into an estate to play golf at midnight, swim in the lake or pick roses – or possibly even for some more nefarious purpose – I would have to carefully line up all the holes. That’s what cunning insurgents of every description do in the movies. Think of how the hero would time the guard patrols, check for blind spots in the CCTV coverage, and/or scout out a spot where a convenient tree grows close to the high wall. These are all holes in the cheese, and what the aspiring intruder will do is line them up so that they can squeeze through each in turn.
And, of course, the job of estate management and estate security is to ensure that there are sufficient slices of cheese, with sufficiently varied a pattern of holes to make it impossible to line them up. Oh I do love a good analogy.
Swiss cheese model in the real world
While Reason’s research was initially about the causes of accidents and catastrophes, it also indicated that human error contributed immensely to a range of system failures in many industries, including manufacturing, medicine, agriculture and finance.
Regardless of the field in which you work, this model can make your organisation more efficient, as well as safer. That’s why we have bookkeepers, accountants, auditors and a finance committee. One talented person could manage the finances perfectly efficiently but no-one is perfect, and there would be no checks to ensure that there were no holes in the ‘cheese’ through which funds may leak.
This works at every scale. When last did you donate blood? You filled in a form, your records were checked on the system, you had your blood pressure and iron checked, and you were issued with a series of barcoded stickers that go on everything associated with you. And then, before the nurse sticks the needle into your arm, they ask you when your birthday is, and check it against the records. That’s the last piece of cheese that prevents your lovely B+ blood from ending up in a sick A+ person.
And, the bigger and more complex the project, the more layers of cheese you need.
*translated into English