Functional Safety for HCI – Proposal for Integration of Human Factors with the IEC 61508 Standard

A. Aas and T. Skramstad (Norway)


HCI, HAZOP, Functional safety, SIL, IEC 61508, System Image.


An Australian study of 75 fatal aeroplane accidents showed that more than 70% of the accidents involved pilot factors [1], i.e. human factors (HF). The needs and roles of human operators in safety critical systems are seldom given adequate focus, compared to the potential risk human factors represent, when humans interact with safety critical systems. Therefore, unsatisfactory consideration of human factors and poorly designed Human-Computer Interaction (HCI) may contribute to compromising safety in ways beyond the designers’ imagination. This paper suggests a possible implementation of human factors into the IEC 61508 (International Electrotechnical Commission), a leading industrial standard for functional safety [2]. Implementation of human factors is suggested performed by dividing the user interface into different levels, representing the whole spectrum of the system safety integrity. Then, each level must fulfil specific demands, based on the effects on the related system’s or subsystem’s safety integrity. One important issue for an operator to operate a system safe and efficient is to have a correct mental model of the system. To achieve this, the operator depends on a correct system image. Providing a correct system image should be one of the main concerns when designing user interfaces for safety critical systems.

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