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7 Elements of a Bowtie Diagram: Bowtie Risk Assessment Explained

Bow tie Risk Assessment Explained

Bowtie Risk Assessment

A strong risk management strategy is essential to the safe and effective operations of any organisation. Risk management involves identifying potential hazards that could lead to an incident and implementing measures to mitigate the potential consequences. An important aspect of risk management is a risk assessment.

There are tools available to help guide risk assessments and prompt critical thinking. Consider conducting a bowtie risk assessment. Bowtie diagrams are a unique visual representation of potential risks and the barriers in place to control them. In this blog, we discuss the significance of bowtie diagrams in risk management and the essential elements that make up a well-constructed bowtie diagram.

Origins of Bowtie Diagrams

Did you know that bowtie diagrams originated in the aviation industry? Bowtie risk assessments were created to assist personnel in visualising complex interactions between various elements that could lead to unwanted incidents, much like what they continue to be used for.  Today, bowtie diagrams have taken off far beyond the aviation industry, used regularly in Oil and Gas, Cyber Security, Mining, Renewable Energies and more.

The 7 Essential Elements of a Bowtie Diagram

A well-constructed bowtie diagram consists of 7 key elements. Understanding these elements is essential for creating an effective representation of risk. Let’s take a closer look at each element and how they fit into a bowtie risk assessment.

 1. Hazard

The hazard is the starting point of the bowtie diagram. It represents a source of potential harm, whether it be an operation, activity, or material. It is something that needs to be contained or carefully handled, so that it does not lead to a loss of control.

For instance, in the context of road safety, the hazard could be “driving a car”.

2. Top Event

The top event is the pivotal point in the bowtie diagram. It’s the moment when control over the hazard is lost, but adverse consequences have not yet occurred. The top event represents the ‘knot’ of our bowtie diagram, and all elements revolve around preventing its occurrence or mitigating the effects once it had occurred.

Using our road safety example, the top event would be “loss of control of the vehicle”.

A common mistake that is often made when creating a bowtie diagram is that the top event actually depicts a consequence, for example “car crash” rather than “loss of control of the car”. Remember, nothing bad has happened at this point. We still have time to mitigate the impacts of the loss of control.

3. Consequence

Consequences represent the undesirable outcomes that could result from the top event. These can range from environmental damage to injuries, damaged reputation, or even loss of life. Identifying and understanding potential consequences is crucial for effective risk management. Measure the severity of each consequence by using a standard or custom risk matrix.

Road safety consequence: “collision with object or other vehicle”.

4. Threat

Threats are sources of harm that could lead to the top event. Threats could be the result of a failure, an external influence or operational issues. They can include system malfunctions, human errors, or external factors that increase the likelihood of the top event occurring. Any one threat must have the power to cause the top event on its own.

Road safety threat: “poor road conditions”.

5. Mitigative Barrier

Mitigative barriers are controls and strategies aimed at reducing impacts of the consequences once the top event has occurred. Located on the right side of the diagram, they play a crucial role in minimising harm and facilitating effective response to the incident. We can’t always prevent an incident from occurring, but we can do our best to mitigate its consequences.

In the context of road safety, an example of a mitigative barrier would be “airbag system”, which could prevent or mitigate an injury or loss of life in the event of a crash.

6. Preventative Barrier

Preventative barriers are the measures put in place to prevent the top event from occurring, located on the left side of the diagram. These can include safety features, protocols and training programs designed to maintain control over the hazard. If the preventative barriers work as intended, the mitigative barriers do not need to be deployed, and all consequences can be avoided.

Road safety preventative barrier: “brakes” or “defensive driving techniques”.

Some barriers could appear in multiple areas on a bowtie diagram. For example, “defensive driving techniques” could both prevent a driver from losing control of the vehicle, and mitigate the consequences if they do lose control. In this instance, the barrier can be defined as both a preventative and mitigative barrier.

7. Degradation Factor

Degradation factors, also known as escalation factors, are conditions or situations that can compromise the effectiveness of barriers. They should be used sparingly and represent only the most significant threats to barrier integrity. Degradation factors differ from threats in that they are attached to a specific barrier.

For example, in road safety, “not wearing a seatbelt” could be an escalation factor that would lead to the failure of the barrier “wearing a seatbelt”.

Bonus: Degradation Controls

Just as there are barriers to threats and consequences, there are also barriers specifically designed to address degradation factors. These are measures put in place to counteract the conditions that might lead to the failure of existing barriers. Each degradation factor should be equipped with a barrier to reduce the chances of the associated barrier failing.

Building off the above example, an degradation factor barrier could be “seatbelt alarm” that encourages the driver and passengers to wear their seatbelt.


Bowtie diagrams are a powerful tool for risk management that offer a complete view of potential threats and consequences and the measures in place to prevent an incident or mitigate its consequences. When conducting a bowtie risk assessment, it’s important to remember that barriers are a central aspect of bowtie diagrams, but they are just one part of the overall picture. Each element contributes to the overall picture of your risk and should be constructed with this in mind.

When creating a bowtie diagram, clear, concise wording of each element and attention to detail are essential. It’s not just about identifying the elements but also about depicting their relationships to other elements of the bowtie diagram accurately. By implementing an effective bowtie risk assessment into your regular risk management strategy, professionals can better visualise and manage risks, creating a more robust risk management system and overall safer organisation.

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This blog was written with references from the Energy Institute’s book, Bow Ties in Risk Management (2018).