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Safety depends on layers, not perfection
The Swiss-cheese model explains accidents as the alignment of weaknesses across several protective layers.
The idea
Each defence—training, procedures, technology, supervision—has gaps. An incident can occur when active errors and hidden system weaknesses line up at the same moment.
An example
A checklist may catch a setup error, but if time pressure, unclear roles, and a missed cross-check align, several defences can fail together.
Put it into practice
After an error, look beyond the final person involved and ask which earlier barriers could have prevented it.
Further reading: James Reason · BMJ ↗
Test yourself: In the Swiss-cheese model, an accident occurs when…
Weaknesses across several defences align
Correct. Safety failures usually involve several gaps lining up, not one isolated cause.
Explanation and illustrative examples by One Card Wiser. Source linked for further reading.
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