Risk modelling is the process of representing the occurrences of failures, errors or circumstances that together can cause an undesirable result such as an accident. Typically, graphical models such as fault trees and event trees are used.

Fault trees look at accident causation to predict the frequency of an accident; event trees look at how an accident might escalate to cause more serious consequences.

Probability theory is used to quantify fault and event trees, to provide numeric estimates of accident frequency and loss.

Sotera differs from other consultancies by:

• Ensuring that risk is modelled at an appropriate level of detail, which often involves modelling local systems, not averaging probabilities across a much wider operation (which tends to underestimate the result).
• Having a wealth of experience of developing risk models for such issues as loss of containment of process fluids and runaway reactions in the process industry and collisions, derailments, fires and track worker accidents in the railway industry.
• Providing databases detailing the derivation of inputs.

Where traditional fault and event tree analysis are not appropriate the application of more unusual techniques, such as Monte-Carlo simulation is used.