Westrum’s Regular, Irregular & Unexampled risks (via Hollnagel)

Not much to say here – I like, and have used for many years, this distinction from Westrum on regular, irregular and unexampled threats.

Has corollaries with other frames, like Rumsfeld’s known unknowns and others.

Extract taken from one of Hollnagel’s presentations (hope he doesn’t mind…) – but Hollnagel, as always, can explain things far better than I.

· Regular: “Events that occur so often that the system learns how to respond” and where “Effective and affordable responses can be prepared”

· Irregular: “One-off events, but so many and so different that it is practically impossible to provide a standard response”. These typically “require improvisation and are not affordable”

· Unexampled: “virtually impossible to imagine and exceed the organisation’s collective experience (Chernobyl, 9/11, subprime crisis) Responses require the ability to self-organize, formulate and monitor remedial actions”

Image & text source: Hollnagel, 2008. From regular threats to unexampled events: Risk, vulnerability, and complex systems. SINTEF

Hollnagel’s presso: https://www.sintef.no/globalassets/project/samrisk/decris/meetings/hollnagel_decris_slides.pdf