Analysis of safety requirements in the context of system faults and human errors

This paper describes an approach to the incremental and iterative analysis of requirements for safety-critical systems. Safety strategies are developed to ensure that hazard states are avoided and the system's integrity is maintained in the presence of failures in the system components. The approach supports an understanding of human error and the formulation of human error tolerance requirements ensuring that safety is preserved in the presence of user errors. The approach is illustrated with an example from the aerospace industry.