What is a Bowtie Analysis?
A bowtie diagram is a risk management tool that visualises risks. With the diagram’s shape resembling a “bow tie.” The bowtie analysis is used to map out the relationships between potential threats, a central event (also known as the top event), and the resulting consequences. The diagram incorporates preventive measures to stop threats from causing the main event and mitigating (or corrective) measures to reduce the impact of these consequences. This makes it particularly useful for managing construction risks such as machinery accidents, fires on construction sites or falls from height.
Go here for the embedded bowtie: Collapse of Excavation Walls Bowtie – OpenRisk
Figure 1 A standard bowtie layout with preventive and corrective barriers
Components of the bowtie model
- Top Event: The central event where control over a threat is lost.
- Threats: Potential causes that can lead to the top event, displayed on the left side of the diagram.
- Consequences: Potential outcomes if the top event occurs, shown on the right side.
- Barriers: Measures placed on both sides of the top event to prevent or mitigate risks. Preventive barriers are on the left, while mitigative barriers are on the right.
Visit this article for a more detailed explanation of the bowtie methodology.
Why Use Bowtie Analysis in Construction?
The bowtie methodology was originally developed in the petrochemical industry, but has since proven a valuable tool in other high-risk industries as well. Construction projects often involve major accident risks, making the need for risk management critical. The possibility of major accidents, the numerous activities and many stakeholders make the bowtie methodology particularly relevant for construction. Site safety benefits greatly from visual tools like bowties, which support clear communication and structured planning across teams. Using a bowtie software tool like OpenRisk enables construction teams to easily create, adapt and share bowtie diagrams tailored to their specific risks, improving collaboration and consistency in risk management.
The main benefits of using the bowtie methodology for construction are:
1. Prevention of accidents and mitigation of consequences: Bowties provide a holistic risk picture by incorporating both preventative and corrective measures. This helps identify both ways of preventing an accident and handling the negative consequences if the accident occurs.
2. Improving risk communication: Risk communication is the process of exchanging information to improve the understanding of risks. A bowtie helps understand risks by visualising the threats, consequences and barriers in one picture.
3. Enhancing Safety Culture: The bowtie methodology promotes a proactive approach to safety, encouraging continuous monitoring and improvement of safety measures. It also helps stakeholders understand and take ownership of their roles in risk management, thereby fostering a strong safety culture within the organisation.
Conducting a Bowtie Analysis
1. Hazard Identification: Begin by identifying the potential hazards in the construction project. Consider the following sources when identifying hazards:
- Expert judgment: Assemble a team of diverse subject matter experts to brainstorm relevant hazards.
- Industry Checklists: Use industry standards and checklists to identify relevant hazards
- Historical data: Use previous inspections, audits, near misses and accidents to identify relevant hazards. This includes past events involving construction explosions, overheating equipment or HVAC construction failures.
2. Define the Top Event: The top event is often considered a ‘critical’ or ‘central’ event. The ‘right’ top event is context-dependent and does not necessarily have to be the worst-case event. It is an event that is central to the bowtie, meaning that it can lead to (many) different negative consequences.
3. List Threats and Consequences: Identify what could cause this top event and potential consequences.
4. Develop and Evaluate Barriers: Identify barriers that can prevent threats from causing the top event or mitigate the consequences. Regularly test and maintain these barriers to ensure their effectiveness. Construction safety training and consistent site safety routines are essential to ensure barriers remain functional and trusted by all teams.
Practical Application in Construction
In construction, Bowtie Analysis can be used for various scenarios such as assessing the risks associated with heavy machinery operations, scaffolding, excavation, and structural work.
In the example below a Bowtie Analysis is made to manage the risk of excavation operations. The top event is the collapse of excavation walls, with threats including bad weather, vibrations or damaged utility pipes. Barriers would include monitoring, operator training, and bracing. Consequences might include worker injury or project delays, with mitigative barriers like emergency medical response and contingency planning.
Click on image to explore the bowtie or go to OpenRisk.presight.com to make your own bowtie in our OpenRisk bow tie software.
Conclusion
A bowtie analysis is a valuable tool for risk management in construction. By implementing this methodology, construction companies can enhance their risk communication, improve safety performance, and foster a proactive safety culture.
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