The Swiss Cheese model, pt. 1

Have you head of the Swiss Cheese model? You see it sometimes in descriptions of how complex systems fail. The visual usually goes like this: The whole idea is: even if you have multiple layers of safety – like many slices of cheese – there are always holes in each slice. Typically, a hole in any slice is covered by a non-hole in the previous one or the next one. (For example, a car might not allow you to grab your keys if you have not shifted to park – or, if you start driving with a handbrake on by accident, the car might yell at you.) But occasionally, the holes just happen to line up, and a larger disaster strikes. The model is used in analyses of past accidents, and prevention of future ones. It has proponents and detractors. It’s hard to talk about its applications because the most common examples are horrific. In my book, I wrote about Therac-25, and that was a really unpleasant chapter to research and to write. Other go-to case studies are equally bleak: Chernobyl, Challenger,…