Compliance with some safety standards (e.g., IEC 61508, CENELEC EN 50126, EN 50128, EN 50129) requires the provision of an Independent Safety Assessor (ISA). ISAs are also used in conjunction with other standards (e.g., FRA 49 CFR Part 236 Subpart H).
The Independent Safety Assessor overseas both system safety and software safety. This in itself can be a tall order since this person must be an expert in both of these areas.
The Independent Safety Assessor provides an opinion on the adequacy of the safety management activities. The ISA works is to provide an independent safety assessment, via safety audits, and the provision of Independent Safety Assessment Reports. Completeness and robustness of the system safety arguments and safety case are their focus. This person though is independent of their company's system safety and software safety groups. In addition, they report to a position high within the company. The Independent Safety Assessor also interfaces directly with the customer's safety people and is intended to provide an impartial overview.
Needless to say, the credentials of this person must equal or exceed those of their own company's safety personnel and must be capable of holding their own in conversations and meetings with the customer. This said, there are many poor ISAs out there. Some can sing the song, dance the dance but when it comes down to detailed experience with system safety and software safety artifacts, they are sadly lacking.
Due to its extensive expertise, experience and the caliber of its people, HCRQ is often sought out to perform this service. HCRQ's services are often requested for SIL 4 applications where the following are mandatory:
- Safety Plan
- Safety Requirements Specification
- Risk Analysis
- Hazard Log
- Markov Analysis
- Cause Consequence Analysis
- Common Cause Analysis
- Interface Hazard Analysis
- Safety Case