Impact and the design of the human-machine interface

We consider the concept of the impact of an action or human error. We begin from an informal definition of impact as: the effect that an action or sequence of actions has on the safe and successful operation of a system, and develop a quantitative measure of the impact of specified behaviours. It is important that human machine interface (HMI) designers should understand the relationship between operator actions and the hazards associated with a system. We demonstrate how impact can be assessed prior to, or in parallel with the design of the HMI, and show how impact assessments could be used to allow risk analysts to inform HMI designers about the relationship between operator actions and system hazards. To illustrate our approach we present a simple case study