Bowtie Risk Analysis
Also known as: Bowtie Method, Bowtie Diagram, Barrier Analysis
A visual risk analysis method that maps the causes and consequences of a risk event, along with the preventive and mitigative controls (barriers) in place, creating a complete picture of risk management.
Quick Reference
Memory Aid
Threats → [Prevention Barriers] → TOP EVENT → [Mitigation Barriers] → Consequences. Shape of a bowtie.
TL;DR
Bowtie analysis maps threats (left) and consequences (right) around a central risk event, with preventive barriers on the left and mitigative barriers on the right. Assess each barrier for effectiveness. Use it to identify control gaps and communicate risk management visually.
What Is Bowtie Risk Analysis?
Draw a bowtie shape: threats on the left, a hazard event in the center, consequences on the right. Then add preventive barriers (left side) and mitigative barriers (right side) to show how you manage the risk.
On Visualizing Risk
If you can't describe what you are doing as a process, you don't know what you're doing.
— W. Edwards Deming, quality management pioneer
The Bowtie method provides a visual representation of risk in a single, easy-to-understand diagram. The hazard or risk event sits at the center (the knot of the bowtie). On the left side, threats (causes) are listed with preventive barriers (controls that stop the event from occurring). On the right side, consequences are listed with mitigative barriers (controls that reduce the impact if the event occurs). Each barrier can be assessed for effectiveness, creating a clear view of risk control adequacy.
Bowtie Diagram Structure
The characteristic bowtie shape showing threats converging through preventive barriers to a central event, then diverging through mitigative barriers to consequences.
The characteristic bowtie shape showing threats converging through preventive barriers to a central event, then diverging through mitigative barriers to consequences.
Origin & Context
Originally developed for the oil and gas industry to visualize process safety risks after the Piper Alpha disaster. Now used across many industries.
Core Components
Hazard/Top Event
The central risk event being analyzed — the moment where control is lost.
Example
Top Event: 'Loss of containment of hazardous chemical from storage tank.'
Threats (Causes)
The various causes or scenarios that could lead to the top event occurring.
Example
Threats: Corrosion, operator error, equipment failure, external impact, overpressure.
Preventive Barriers
Controls and safeguards that prevent threats from causing the top event.
Example
Barriers: Corrosion inspection program, operator training, pressure relief valves, protective bollards.
Consequences
The potential outcomes if the top event occurs.
Example
Consequences: Environmental contamination, worker injury, regulatory penalty, reputational damage.
Mitigative Barriers
Controls that reduce the severity of consequences if the top event occurs.
Example
Barriers: Containment bunds, emergency response plan, medical facilities, insurance coverage.
Did You Know?
The Bowtie method gained global prominence after the Piper Alpha disaster in 1988, which killed 167 workers on a North Sea oil platform. Investigation revealed that multiple preventive barriers had failed simultaneously. Royal Dutch Shell subsequently championed the bowtie approach, and today it is mandatory in the oil and gas industry in countries including Australia, the Netherlands, and Norway.
When to Use Bowtie Risk Analysis
Process safety management
Problem it solves: Complex safety risks are difficult to communicate and manage holistically.
Real-World Application
A chemical plant creates bowtie diagrams for its top 10 major hazards, displayed in control rooms for operator awareness.
Operational risk management
Problem it solves: Organizations need to visualize the adequacy of their risk controls.
Real-World Application
A bank uses bowtie analysis for its top operational risks (cyber attack, fraud, IT failure), identifying where barriers are weak.
Regulatory demonstration
Problem it solves: Regulators require evidence that risks are understood and controlled.
Real-World Application
An airline presents bowtie analyses during regulatory audits to demonstrate comprehensive risk management for critical safety scenarios.
Barrier Quality Matters
A barrier is only as good as its effectiveness. Assess each barrier for: independence, reliability, auditability, and whether it requires human action (less reliable) or is automated (more reliable).
How to Apply Bowtie Risk Analysis: Step by Step
Before You Start
- →A specific risk event to analyze
- →Knowledge of the threats and consequences
- →Understanding of existing controls and barriers
Define the top event
Identify the central risk event — the moment where things go wrong.
Tips
- ✓Be specific: 'loss of containment' not 'safety incident'
- ✓Place it at the center of your diagram
Common Mistakes
- ✗Making the top event too broad or too narrow
Identify threats
List all the causes or scenarios that could lead to the top event.
Tips
- ✓Use brainstorming, historical data, and incident reports
- ✓Include both internal and external threats
Common Mistakes
- ✗Listing only obvious threats; missing systemic or combined causes
Map preventive barriers
For each threat line, identify the controls that prevent the threat from causing the top event.
Tips
- ✓Assess each barrier's effectiveness and reliability
- ✓Identify gaps where barriers are missing
Common Mistakes
- ✗Listing barriers without assessing their effectiveness
Identify consequences and mitigative barriers
List the potential consequences and the barriers that reduce their severity.
Tips
- ✓Consider the full range of consequences: safety, financial, reputational, regulatory
Common Mistakes
- ✗Focusing only on prevention and neglecting mitigation
Assess overall adequacy
Review the complete bowtie to identify weak spots, missing barriers, and areas for improvement.
Tips
- ✓Look for single points of failure — threats with only one barrier
Common Mistakes
- ✗Not acting on the insights — the bowtie should drive improvement actions
Value & Outcomes
Primary Benefit
Provides a clear, visual representation of how risks are controlled, making risk management tangible and communicable.
Additional Benefits
- ✓Identifies control gaps and single points of failure
- ✓Excellent communication tool for diverse audiences
- ✓Supports both prevention and mitigation planning
What You'll Learn
- →How to decompose complex risks into manageable elements
- →How to assess the adequacy of risk controls
- →How to communicate risk management visually
Typical Outcomes
Best Practices
📋 Preparation
- •Gather relevant incident data and risk assessments before the session
- •Involve both subject matter experts and operational staff
🚀 Execution
- •Keep each bowtie focused on one specific top event
- •Assess barrier effectiveness, not just existence
- •Use consistent criteria for barrier quality assessment
🔄 Follow-Up
- •Address identified control gaps with specific action plans
- •Review and update bowties after incidents or changes
- •Display bowties where operational staff can reference them
💎 Pro Tips
- •Color-code barriers by effectiveness (green=strong, amber=adequate, red=weak) for visual impact
- •Link barrier effectiveness to your KRI monitoring system
Bowtie analysis excels at communication. A single diagram can explain a complex risk to boards, regulators, and front-line workers in a way that a 50-page risk assessment cannot.
Aviation Safety: The Swiss Cheese Model in Practice
After the 2009 Air France Flight 447 crash, the French Bureau of Investigation and Analysis used bowtie analysis to map how multiple barriers failed: the pitot tube icing (threat) was not prevented by redundancy (barrier degraded), and pilot response (mitigative barrier) failed due to inadequate training for manual flying at high altitude. The resulting bowtie diagrams drove industry-wide changes to pilot training requirements and sensor redundancy standards.
Limitations & Pitfalls
Represents a static view of risk at a point in time
Mitigation: Review and update bowties regularly, especially after incidents or organizational changes
Can become overly complex for risks with many threats and consequences
Mitigation: Focus on the most significant threats and consequences; create separate bowties for sub-risks
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