Risk Analysis, Impact and Interaction Modelling

Operator error has been blamed for many accidents and incidents in safety-critical systems. It is important that human-machine interface (HMI) designers are aware of the relationships between their design decisions, operator errors, and the hazards associated with a system. In this paper, we demonstrate how information from risk analysis can be combined with formal specification of the HMI, to support designers in exploring these relationships. We use the concept of interactor to model the human-machine interface (HMI); together with a concept of impact, which we define informally as: “the effect that an action or sequence of actions has on the safe and successful operation of a system.” We show how interactors can be used as design representations for the HMI at the earliest stages of design, as well as providing a medium by which risk analysts can inform HMI designers about the impact of human-errors. To demonstrate the feasibility of this approach, we consider a simple, gas-fired, electricity generating plant as a case study. Our proposed approach is intended to complement, rather than compete with, existing design and analysis methods for the HMI. The method achieves this by making risk analysis information available in the early stages of HMI design.