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Safety-related systems in road vehicles are subject to hazard analysis as part of developing their safety requirements. Automotive hazard analysis leads to a requirement for target risk reduction in the system to be developed, usually expressed as a safety integrity level, SIL, or ASIL. During risk analysis, credit can be taken for risk reduction from facilities outside the system of interest, or from architectural decisions to distribute the required risk reduction to sub-elements of the system. Up to now, such concepts have been presented in standards without any justification. The different approaches in the standards are discussed, and a scheme for more rigorously defining the allocation of safety integrity requirements across different elements of a system is proposed.

With the increasing dependence on advanced electronic systems to control the functionality of road vehicles, the consideration of functional system safety as part of the design and implementation process for these systems is growing in importance. An important part of such a process is to undertake a hazard analysis. Emerging standards and guidelines, such as ISO 26262 and MISRA Safety Analysis, contain a requirement to perform preliminary hazard analysis in order to identify unwanted events (typically at the vehicle level) that can result from technological causes, and to set safety requirements for the system under development to mitigate the risk associated with those events. In this paper, a generic approach to automotive hazard analysis is described. The method is based upon a generalized model of the causal chain that leads from a low-level fault in an electronic system through to the potential for an unwanted event at the vehicle level.

As the discipline of Functional Safety spreads from its traditional industries such as process and aviation to the automotive sector, this paper - based on the MISRA Safety Analysis Guidelines - describes how a functional safety lifecycle can be applied in a way which is both appropriate for automotive systems and aligned with international standards such as IEC 61508.