What differentiates ISO 26262 from other Functional Safety standards derived from IEC 61508 is the notion of Safety Goal: i.e., ISO 26262 is essentially Goal-Oriented. A Safety Goal is a high-level, articulated safety requirement.
Safety Goals are result of HARA (Hazard Analysis and Risk Assessment and must be accompanied by (at least)
- ASIL (Automotive Safety Integrity Level)
- Safe State
- FTTI (Fault-Tolerant Time Interval)
What must be kept in mind is that, despite they will generate a sequence of detailed requirements during lifecycle (Functional, Technical, SW/HW Safety Requirements), Safety Goals have to be considered during each activity: for example, safety mechanisms and safety paths (part 4) must be defined per Safety Goal; a Safety Analysis on Technical Safety Concept and Safety Architecture (Part 4 of the standard), or SW Safety Analysis (part 6), or FMEDA on HW architecture and design (part 5), must prove that no Safety Goal is violated. And so on…
This is of course also true in Safety Validation and in the emission of Safety Case. In the latter, the safety manager must demonstate that the required risk reduction has been obtained for each safety goal originated in HARA, through all the activities required by ISO 26262 for that ASIL.
Stay in touch for more on Safe State and FTTI!!!
