The first step in FuSa design is the item definition. The item is the top‑level vehicle function or subsystem that will be the subject of functional‑safety analysis. The objectives of item definition are:

• Define and describe the item, its dependencies on, and interaction with the environment and other items.

• Support an adequate understanding of the item so that the activities in subsequent phases can be performed.

This step incorporates hazard analysis and risk assessment (HARA), a systematic methodology that transforms identified functional hazards into quantified Automotive Safety Integrity Levels (ASILs) and corresponding safety goals. The HARA process establishes clear traceability to the item definition while providing a risk-based foundation for all subsequent safety activities. The primary objectives of HARA include:

• Identify all potential hazardous events that could result from the item.

• Rigorous risk assessment through detailed analysis of each hazard's severity, exposure probability, and controllability factors.

• Assignment of appropriate ASIL classifications based on the assessment results.

Hazard identification can be carried out using techniques such as Failure Modes and Effects Analysis (FMEA), Hazard and Operability studies (HAZOP), or lessons learned from past quality problems. Each identified hazardous event is then evaluated for Severity (S), Exposure (E) and Controllability (C) and assigned an ASIL. The appropriate ASIL for each event can be derived from the matrix shown in Table 1-3.