Practical early-lifecycle application of human factors assessment

Human Reliability Analysis (HRA) is often seen as a time consuming task, which requires significant expertise. This may lead to a reduced focus on the human in the loop, and a failure to consider both where human error and recovery may impact on system safety performance. Through the use of a case study involving a Positive Train Control (PTC) driver interface, this paper aims to examine whether early system architecture phase task analysis can produce meaningful results with little time overhead or human factors expertise. The approach which has been used was to conduct a task analysis on a system sequence diagram, identifying the high order goals and the individual driver tasks, including alternate paths. Once this task analysis was completed, a tailored FMECA was conducted to identify human failure modes which may lead to system hazards and to thereby limit the scope of the subsequent HRA. The criticality analysis was performed via a HEART analysis to estimate error likelihoods, and which also identified risk factors in the HMI design and operating environment. The outcomes of the case study were design requirements on the resulting driver interface, in addition to operating procedures, and training requirements. It is argued that the approach presented allows for an analysis to be conducted early in a system design lifecycle at low cost and with limited expertise, which adds to the overall safety argument for the end product.