System Safety Case

A System Safety Case (SSC) is a structured, evidence-based argument that a system is acceptably safe for a defined use, in a defined context, supported by documented analysis, verification, validation, and risk controls.

Expanded Explanation

1. Technical Function and Core Characteristics

A SSC documents safety claims about a system, the supporting safety argument, and the body of evidence that demonstrates how the system meets defined safety requirements and target risk levels. It typically includes hazard identification, risk assessment, safety requirements, Verification and Validation (V&V) results, and traceability across the system lifecycle.

Formal guidance from defense, transportation, and standards bodies describes a safety case as an explicit, structured argument, often represented using graphical or tabular notations, that links safety objectives to analyses, tests, and operational data. It usually defines the system context, operational assumptions, dependencies, and safety constraints so reviewers can evaluate whether the claimed level of safety is justified.

2. Enterprise Usage and Architectural Context

Enterprises use system safety cases in sectors where system failure can cause harm, such as aviation, rail, automotive, industrial automation, energy, and medical devices. In these contexts, the safety case supports regulatory approvals, certification, and internal governance by demonstrating that the system architecture, design decisions, and controls address identified hazards and risks.

Within enterprise architecture, the safety case often integrates with model-based systems engineering, systems-of-systems analysis, and safety management systems. It references architecture descriptions, hazard logs, failure modes and effects analyses, software assurance artifacts, and operational procedures, and it is updated as the system changes, new hazards are discovered, or operating conditions evolve.

3. Related or Adjacent Technologies

System safety cases relate to safety standards and frameworks such as those for functional safety, software and hardware safety, and sector-specific safety regulations for transportation and healthcare. These standards often require or endorse a safety case approach to show compliance with risk targets and lifecycle processes.

They are also connected to assurance cases in other domains, such as security assurance cases and dependability cases, which use similar structured-argument methods to justify claims about properties like cybersecurity, reliability, or resilience. Common notations and methodologies, such as goal-structured argumentation, provide a shared basis for constructing and reviewing these assurance artifacts.

4. Business and Operational Significance

For organizations, a SSC provides a traceable, auditable record of how safety risks were identified, analyzed, and controlled across development and operation. It supports regulatory compliance, internal risk management, and due diligence by documenting the rationale behind safety-related decisions and residual risk acceptance.

Operationally, the safety case informs change management, configuration control, and incident investigation, because it captures safety assumptions, dependencies, and evidence that may be affected by design changes or field events. It also supports communication among engineering, safety, legal, and executive stakeholders by providing a common structure for evaluating whether a system remains acceptable for use.