Human Factors in the Development of Safety- Critical Railway Systems

SUMMARY Existing CENELEC railway safety standards such as EN50126/9 mandate that human factors be addressed in the entire system lifecycle. In particular, the EN50126 standard has identified the five known human factors influencing the system development process. However, there is growing concern about the adequacy of existing standards and practices on managing these factors. The authors’ empirical studies in the Chinese railway signalling industry have shown that the outcome of different manufacturers using the same SIL development process varies thereby resulting in different safety risks associated with the system under development. This paper discusses the extent to which the human element contributes to the effectiveness of the process implementation and the level of confidence during the system development stages. A number of finergrained human factors such as training, working attitude, stress, project schedule, team management style and enterprise culture and their effect on delivering safety-critical systems solutions have been discussed. Consequently, a human factors evaluation framework is proposed. This framework can be seen as an extension of existing railway safety standards.