The EN 50129 safety case is the structured and documented safety statement that the conditions for safety acceptance have been fulfilled. The safety case includes all safety-relevant aspects of the product life cycle. When creating the document, the challenge is therefore to present a wide range of information in a clear and comprehensible manner. EN 50129 supports you in this by providing a relatively detailed structure for the documentation.
In the following article, I will deal with the key factors relevant to practice for an EN 50129 compliant safety case.
Content and categories of the EN 50129 compliant safety case
EN 50129 specifies the following structure for the safety case in chapter 5:
- Part 1: Definition of the system
- Part 2: Quality management report
- Part 3: Safety management report
- Part 4: Technical safety report
- Part 5: Relationships with other safety cases
- Part 6: Summary
EN 50129 distinguishes between the following 3 categories of safety cases:
- Generic product safety case (independent of the application)
- Generic proof of application safety case, for a class of applications
- Specific proof of application safety cases, for a specific application
For all 3 categories, the structure of the safety case and the procedure for safety approval is essentially identical.
Challenges in preparing the safety case
The challenge lies above all in the clear structuring of the complex information. The information is divided into the categories planning, specification and proof (verification/validation). Planning is usually documented in tools such as MS Word. For the specification, databases are typically used for the requirements and graphical tools for the architecture.
It is impossible to manage all the information of a safety development in one tool, despite different available ALM/PLM tools. However, in order to be able to create a comprehensible and structured safety case, professional tools with a cross-tool easy traceability of the information are crucial.
Tips for a good, comprehensible safety case
The central element for a good safety case is project management. It is one of the central tasks of project management to lead the project pro-actively and with foresight. Such management is expressed in compact but clear plans (safety plan, test strategy plan, etc.).
Another central point is the traceability between the different information. The main artifacts are requirements, architecture, source code, the HW schematic and tests. Here it is especially important to develop practicable strategies for tool interfaces. Traceability between two pieces of information, which are managed in different tools (e.g. architecture and requirements), still requires some experience.
Related HEICON Blog posts
- ISO 26262 Safety Case – Success factors: management and traceability!
- Requirement and Test Traceability – Any added value?
- How many level of Software requirements are necessary and useful?
- Good safety development process – What is it?
- Management aspects of testing
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