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In this episode of Risk! Engineers Talk Governance, due diligence engineers Richard Robinson and Gaye Francis discuss the mathematics behind risk modelling and why relying on heat maps for decision-making can have limitations.

Richard and Gaye explore the concept of the "ideal" hazard risk curve, unpacking why every hazard carries its own unique risk profile rather than a neat line of constant risk. Drawing on Heinrich's accident triangle and the hyperbolic relationship between consequence and likelihood, Richard walks through the calculus of integrating under a risk curve, and why simply "spotting the dot" on a five-by-five risk matrix can underestimate high-consequence, low-likelihood events by an order of magnitude or more.

They discuss the limitations of the standard risk matrix for large organisations dealing with vastly different scales of risk, and why New Zealand's updated WHS legislation is shifting focus toward identifying critical hazards and credible controls first, rather than getting bogged down debating likelihood.

Key takeaways:

• Heat maps are useful for communication, but dangerous as standalone decision-making tools
• The area under the risk curve matters – it's far larger than a single dot suggests
• Safety risk assessment should prioritise critical hazards and reasonable controls over likelihood arguments

Note: This episode references slides — for the full visual experience, check out the YouTube channel https://www.youtube.com/c/R2aAu.

If you’d like us to cover a specific topic or have any feedback we’d love to hear from you. Email admin@r2a.com.au.

For further information on Richard and Gaye’s consulting work with R2A, head to https://www.r2a.com.au, where you’ll also find their booklets (store) and a sign-up for their quarterly newsletter to keep informed of their latest news and events.

Gaye is also founder of Australian women’s safety workwear company Apto PPE https://www.aptoppe.com.au.