The following is an edited transcription of an interview with me conducted by Dr Howard Morris of Safe Work Australia in 2016. The web link to this interview is no longer available, so I have been free with my editing to improve readability and in places expand on content.
Derek Viner August 2025
THE RISK MATRIX
Dr Howard Morris
I understand you have issues in relation to use of the risk matrix. Can you explain these, please?
Derek Viner
My concerns with the risk matrix are threefold. The first one is that I think it’s a misdirected effort. In an earlier question, maybe the first question, you asked me what I thought the goal was and I said it was to achieve the right standards of risk control. The goal is in no way to try to work out what level of risk are we managing.
That’s that’s not what legislative obligations in Workplace Health and Safety are asking of us. They’re asking of us to achieve the right standard of control over a risk. So trying to identify or trying to estimate the level of risk in a matrix is not actually what’s required of us and using a matrix to then determine what management effort is needed as a result of that is just a building onto something which shouldn’t have a foundation at all. So number one, it’s misdirected efforts, not what we’re here to do.
Number two, it’s not a suitable tool for the estimation of risk. It’s not possible to judge what likelihood is on a simple word scale with any meaning at all. Likelihood is a synonym for probability. It is sometimes used in a Risk Matrix as a synonym for frequency. Probability and frequency are two different things.
The two, Frequency and Probability, are related by Exposure to the circumstances in which it could happen, and in using scales of likelihood, one is not giving explicit recognition to this fact. Risk matrix word scales and their explanations sometimes confuse Probability and Frequency in any event.
This second point is that a simple matrix doesn’t adequately represent what is, in reality, a logarithmic relationship between likelihood and consequence value, and in asking somebody to pick a single cell of the matrix carries a misunderstanding of what risk is. Risk is actually a relationship between frequency and consequence value. It is quite commonly understood that high frequency but low consequence things, and low frequency and high consequence things arise from the same risk. And so risk is this relationship. The Matrix doesn’t help to make this evident, and so it’s often incorrectly used.
The third point I’d like to make about it is that my own research with colleagues, and anecdotal experience in industry, is that the risk matrix is incapable of consistent use, either between groups of people or individuals or even from the same person over a different over a period of time.
So I think these are three significant reasons why the risk matrix is not something which should be the focus of activity.