Generalized formula for the calculation of a probabilistic metric for random hardware failures in redundant subsystems

The introduction of International Organization for Standardization (ISO) standard 26262 “Road vehicles — Functional safety” in 2011 provided a state-of-the-art methodology for achieving functional safety in automotive electrical and/or electronic (E/E) systems. The standard defines the probabilistic metric for random hardware failures (PMHF) as the average probability of a violation of a safety goal associated with a failure over a vehicle's lifetime and architecture metrics. Although a PMHF formula is provided, the explanation of the standard is insufficient. In this paper, we propose a method to calculate the PMHF and expand the application to redundant subsystems that are not adequately described in the standard.