Bowtie analysis

Category: Risk identification & assessment · Reviewed by Mark Fox, Broker · Renewals · Last reviewed

Bowtie analysis

Bowtie analysis is a visual risk assessment technique that links the causes of a hazard, through a central “top event”, to its consequences and the controls placed at each side. The diagram resembles a bowtie — hence the name. It was developed within Shell in the 1970s and is now codified in CCPS guidance and IEC 31010.

Anatomy

• Hazard — the source with potential to cause harm (e.g. “stored flammable liquid”).
• Top event — the loss of control over the hazard (e.g. “release of flammable liquid”).
• Threats (left side) — the causes that could lead to the top event.
• Consequences (right side) — the outcomes that could follow the top event.
• Preventive controls (or “barriers”) — placed on threat lines to stop the top event.
• Mitigating controls — placed on consequence lines to reduce loss given the top event has occurred.
• Escalation factors — factors that could degrade individual controls.

Strengths

• Clear visual link between cause, event, consequence and controls.
• Surfaces single points of failure and over-reliance on individual controls.
• Excellent communication tool to non-specialists (boards, regulators, the workforce).
• Naturally maps to the Swiss cheese model of accident causation (Reason, 1990).

Use in insurance

Bowtie diagrams are increasingly seen in cyber, energy, marine and major-hazard insurance submissions. They translate complex risk pictures into a single page underwriters can interrogate.

References

• CCPS (2018). Bow Ties in Risk Management.
• IEC 31010:2019, Annex B.4.
• Reason, J. (1990). Human Error. Cambridge University Press.

Cross-references

• Hazard identification
• Root cause analysis
• HAZOP study

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