Bow-Tie Analysis: A Practical Guide to Visualizing and Managing Project Risk

# Analysis is and why teams use it

# Core concepts, stated simply Hazard: a source of potential harm (for example: stored energy, hazardous chemicals, heavy lifting operations, high-voltage equipment, cybersecurity access, or critical infrastructure failure).

Threats: credible, specific causes of the top event. They should be detailed enough that a meaningful preventive control can be identified (e.g., avoid generic "equipment failure" in favor of "failure of the temporary lifting mechanism due to inadequate inspection").

Mitigating barriers: controls that reduce the severity or likelihood of consequences after the top event. Examples include emergency shutdown systems, fire suppression, evacuation procedures, emergency response teams, containment systems, backup systems, and crisis communications.

Escalation factors: conditions that can reduce barrier effectiveness. A procedure may work normally but fail if personnel are unavailable, communications systems fail, or required equipment is inaccessible. Identifying escalation factors exposes where apparently strong controls can break down under certain conditions.

# How to perform a Bow-Tie Analysis (step-by-step)

1. 1Define the hazard: identify the source of potential harm rather than an undesirable outcome.
2. 2Identify the top event: choose the point that represents loss of control immediately before harm could occur.
3. 3Identify threats: list credible, specific causes that could trigger the top event. Treat each threat independently to find the appropriate preventive controls.
4. 4Identify consequences: list outcomes that could follow the top event (injury, environmental damage, financial loss, schedule disruption, regulatory or reputational impact, or project failure).
5. 5Map preventive barriers: assign controls between threats and the top event. For each barrier, assess whether it can actually interrupt the threat pathway.
6. 6Map mitigating barriers: assign controls between the top event and each consequence to reduce severity or likelihood.
7. 7Identify escalation factors for each barrier and consider controls or redundancies to address those factors.

# Practical points teams should apply

• Be specific. Vague threats or barriers produce weak analyses. Replace high-level labels like "equipment failure" with a failure mode and cause that shows how to control it.

• Use the bow-tie as both a visualization and a checklist for control gaps and escalation scenarios.

# Outcome you should expect A structured bow-tie diagram that clarifies which threats lead to the defined top event, which barriers are intended to stop those threats, and which mitigating measures limit consequences. The work highlights weak or single-point-of-failure controls and surfaces escalation factors that require additional attention.