Systematic integration of human factors in the specification of requirements for new railway technologies

Engineering design processes are necessary to attain the requisite standards of integrity for high-assurance safety-related systems. Additionally, human factors design initiatives can provide critical insights that parameterise their development. Unfortunately, the popular perception of human factors as a “forced marriage” between engineering and psychology often provokes views where the ‘human factor’ is perceived as a threat to systems design. Some popular performance-based standards for developing safety-related systems advocate identifying and managing human factors throughout the system lifecycle. However, they also have a tendency to fall short in their guidance on the application of human factors methods and tools, let alone how the outputs generated can be integrated in to various stages of the design process. This case study describes a project that converged engineering with human factors to develop a safety argument for new low-cost railway level crossing technology for system-wide implementation in Australia.The paper enjoins the perspectives of a software engineer and cognitive psychologist and their involvement in the project over two years of collaborative work to develop a safety argument for low-cost level crossing technology. Safety and reliability requirements were informed by applying human factors analytical tools that supported the evaluation and quantification of human reliability where users interfaced with the technology. The project team was confronted with significant challenges in cross-disciplinary engagement, particularly with the complexities of dealing with incongruences in disciplinary language. They were also encouraged to think ‘outside the box’ as to how users of a system interpreted system states and behaviour. Importantly, some of these states, while considered safe within the boundary of the constituent systems that implemented safety-related functions, could actually lead the users to engage in deviant behaviour. Psychology explained how user compliance could be eroded to levels that effectively undermined levels of risk reduction afforded by systems. Linking the engineering and psychology disciplines intuitively, overall safety performance was improved by introducing technical requirements and making design decisions that minimized the system states and behaviours that led to user deviancy. As a commentary on the utility of transdisciplinary collaboration for technical specification, the processes used to bridge the two disciplines are conceptualised in a graphical model.