Bow-Tie Analysis
Definition
A risk-visualisation method combining a fault tree (left of the bow-tie, hazard to critical event) with an event tree (right, critical event to consequences), with barriers drawn explicitly on both sides to show prevention and mitigation.
- Left side
- Fault tree, hazards to critical event
- Right side
- Event tree, critical event to consequences
- Key feature
- Barriers shown explicitly on both sides
- Used for
- Visualising prevention and mitigation controls together
Common questions
What does a bow-tie diagram show that a fault tree alone does not?+
A fault tree alone stops at the critical event, showing only how it could occur. The bow-tie adds the event tree on the right, showing how consequences unfold afterward and what mitigation barriers limit harm, so both prevention and response controls appear on one diagram.
How is bow-tie analysis used in an incident investigation?+
Investigators map which barriers on the diagram were present, which failed, and which were absent for the actual incident, turning a generic hazard model into a specific account of why prevention or mitigation broke down in that event.
Related terms
- Active Failure
- An error or rule violation by a front-line operator whose effects are felt immediately. Active failures are the triggers Reason calls 'unsafe...
- Blowout Preventer (BOP)
- A large specialised valve or series of valves installed at the wellhead of an oil or gas well to seal, control, and...
- Latent Condition
- In Reason's model, a pre-existing organisational weakness (poor design, defective procedure, unrealistic scheduling, inadequate training) that lies dormant until aligned with other...
- Safety Management System (SMS)
- A formal, documented framework of policies, procedures, responsibilities, and performance monitoring through which an organisation identifies hazards, assesses risks, and manages safety...
- Swiss Cheese Model
- James Reason's accident causation model representing each defensive barrier as a cheese slice with holes. An accident occurs when holes in successive...