The risk matrix is the standard risk assessment tool in aviation SMS and other risk management industries. It’s a standard tool because it’s simple and accomplishes all of the needs of a risk assessment, namely:
In this article, we will look review:
Defining criteria for each level of likelihood and severity is what makes your risk matrix so valuable. Doing this ensures that:
Furthermore, defining criteria allows you to “make your risk matrix your own,” so that you are assessing issues with terms that are unique to your organization’s size and needs.
Severity on the risk matrix represents the severity of the most likely consequence of a particular hazard occurrence. In other words, if a hazard occurs and is not mitigated, what is the severity of the most likely problem that will occur? As ICAO says of severity, “the severity... of a hazard’s projected consequence.”
For example, in the event of a hazard “Runway incursion,” the most likely problem that will occur is probably either an Accident or Near Miss. If you determine that an Accident is a most likely probable concern, the severity would be “Catastrophic”. If you determine that Near Miss is the most probable concern, then “Serious” would likely be your severity.
So, when you are defining criteria for severity in your risk matrix, keep in mind that you are defining criteria for the most likely safety incident following a hazard occurrence.
Likelihood on a risk matrix represents the likelihood of the most likely consequence occurring in the event of a hazard occurrence. To put it another way, if a hazard occurs, what are the chances the most likely safety mishap will occur?
To use the example from earlier, in the event of a hazard “Runway incursion,” the most likely problem that will occur is probably an Accident. The likelihood of this occurrence would be fairly low, as many control measures are mitigating this problem.
So, when you are defining likelihood in your risk matrix, you should create criteria that define the likelihood of the risk occurrence (not the likelihood of hazard occurrence).
It’s extremely important that you use multiple different criteria to define severity on your matrix. These criteria will give you multiple modes of justification for each risk assessment’s severity.
Each level of severity should use the same criteria but have an increase in “damages” for each rising level of severity. Here are some ways to define criteria for severity, with some examples below each type of criteria:
You may have additional qualifying elements you wish to define for Severity that are relevant to your organization. Also, your criteria for each level of severity should certainly be different from the examples above – for example, $1m may be “Catastrophic” for small and medium-sized service providers, but may only be “Moderate” severity for a large operator.
When defining likelihood, aviation service providers usually define criteria in one of two ways. These two ways are by either:
In terms of the quantitative approach, for the number of expected occurrences you might define it as:
This can be a good method if you have significant historical data to analyze occurrences per number of operations for specific hazards.
We recommend that most providers use qualitative criteria for defining likelihood, as it’s fairly straightforward and convenient for SMS of all ages and sizes. You might define these criteria as either expected frequency or expected chances of occurrences.
These are just loose examples, and you should define your chances based on the size, complexity, and number of operations in your company.
NOTE: you can set level A as your high likelihood or low likelihood, as there is no set direction your matrix needs to go.
Last updated August 2024.