Quite often, Safety Engineers are confused between Functional Safety requirements (FSR) and Technical safety requirements (TSR). What level of details are to be provided in both the requirements and where exactly to cut the boundaries between these two is unclear. We will discuss the same in this post. Requirements Hierarchy Functional Safety Requirements (FSR) are derived from Item definition, HARA and Safety goals and are traced back to Safety Goals. Each Safety goal shall have a minimum of one FSR associated with it. Technical Safety Requirements (TSR) are mainly derived from FSRs. Each FSR shall have a minimum of one TSR associated with it. The below image provides a hierarchical view of requirements/activities flow from ISO26262 Part 3 – Item definition to Part 5 Hardware Safety Requirements (HSR) and Part 6 Software Safety Requirements. Also visit our YouTube video which explains the flow of Functional Safety requirements. Difference between FSR and TSR This table gives the hig