Risk Evaluation Series

I have never really liked risk assessments that involve some vague calculation of consequence and likelihood. I have witnessed, and perhaps been involved in, many arguments about where to stick some potential or even past disaster into a limited matrix.

A couple of years ago, I had a whinge/thought experiment on an alternative method of risk evaluation. I enjoyed the use of the term Probability-Impact Graph, rather than Likelihood-Consequence Matrix, to create a little theme - see if you can guess what it was.

I’ve repackaged these posts and a follow-up post for renewed consumption below. Each image is actually a link to the post.

My Problem with PIGs

At the time, I had been growing more and more uneasy with the application of the PIG or Probability-Impact Graph or Likelihood-Consequence Matrix. I wasn't seeing, however, the same discontent in others and therefore, started to doubt my own reservations. Luckily, I found some like-minded people over at LinkedIn (membership to both LinkedIn and the group are required to view the actual discussion) with a Mr Stephen Cresswell putting his thoughts on paper here.

Vulnerability & Proximity

The first post was a bit of a whinge about the PIG or as it is more commonly known, the likelihood-consequence matrix. I signed off that post with a promise to further the discussion on the risk matrix within an aviation safety context. Here goes...

Consequence is an inappropriate dimension to consider in aviation safety. For two reasons which I call vulnerability and proximity. Let's take them in turn.

One Step Back...

I had tried a few of these arguments out on some colleagues at work and they seemed unconvinced. So, I took a step back to refine some of my thoughts.

Influential Behaviour

In this post I explored my ideas further using a different accident causation/investigation model - the AcciMap.

Wrapping Up PIGs .... For Now

Since I didn't want to be thought of as some PIG-hating obsessive lunatic, I wrapped up the series with a quick recap. My primary thesis was that the traditional likelihood-consequence matrix (PIG - see original post) is not particularly useful when dealing with aviation safety.

On the Shoulders of Giants

And then a couple of weeks later, I spotted, in a very distinguished person’s presentation, the concepts I had been writing about. Maybe I had seen them before and they sprouted into these posts.

I haven’t come back to this topic to explore the likelihood side of the equation. I have always quite liked the concept of exposure but I do worry that people have a tendency to move the goal posts until they get the answer they like. Perhaps I will re-examine this topic again in the near future.

Let me know what you think, either below in the comments to this post or under the individual posts linked above.