Thinking systemically about safetey

Accidents involve much more than the reliability of parts. Safety emerges from the systemic interactions of devices, people and organizations. Nancy Leveson’s Engineering a Safer World (free pdf currently at the MIT press link, lower left) picks up many of the threads in Perrow’s classic Normal Accidents, plus much more, and weaves them into a formal theory of systems safety. It comes to life with many interesting examples and prescriptions for best practice.

So far, I’ve only had time to read this the way I read the New Yorker (cartoons first), but a few pictures give a sense of the richness of systems perspectives that are brought to bear on the problems of safety:

Leveson - Pharma safety
Leveson - Safety as control
Leveson - Aviation information flow
The contrast between the figure above and the one that follows in the book, showing links that were actually in place, is striking. (I won’t spoil the surprise – you’ll have to go look for yourself.)

Leveson - Columbia disaster

2 thoughts on “Thinking systemically about safetey”

  1. I came across Nancy Leveson’s STAMP a while back when doing a study for NASA. She certainly had some good ideas then and I’m glad to see how they’ve grown. The study we did didn’t end up going anywhere unfortunately, but we did model some of the “normalization of deviance” that Diane Vaughan discussed in the report on the STS Columbia accident. It’s not a great paper, but I think there are still some interesting insights into how time and delays eat away at even the most well designed safety protocols. It’s available online here:

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