People and Systems: Striking a Safe Balance between Human and Machine

Humans may be viewed as being merely fallible operators of machines; however, that technology-centred view can easily understate the ability of the human to perform tasks which most machines are incapable of doing and to intervene in the event of failure. On the other hand, an overly human-centred view may not take full advantage of the ability of machines to carry out numerically-complex, repetitive tasks consistently and at relatively high speed, and to provide alerts in the event of failure on the part of the human. Somewhere between these extremes lies a more balanced, integrated approach in which the best (and worst) characteristics of human and machine are fully recognised in the development of safe system solutions. This paper, produced in support of a tutorial entitled: ‘System Safety Requirements for People, Procedures and Equipment’, given at the Safety-critical Systems Symposium 2006, presents a generic approach for the specification and realisation of safety requirements for both technical and human elements of safetyrelated systems.