Independent Safety Assessment of Rail Systems in their Operational Environment
There is an increasing use of Programmable Electronic Systems (PES) in safety related applications: some of these, including many rail systems, are large and complex. Emerging standards, and some of the regulatory authorities, require that the safety of such systems is checked independently: this is the role of the Independent Safety Assessor (ISA) which we are carrying out on behalf of two railways in Hong Kong. We believe it important that the ISA should examine the technical changes, human operation changes and technical/human changes required as a consequence of the use of the new system in the operating environment of the railway because these changes may impact safety. Our work as ISA covers audits of the development process, auditing of plans and of the adaptation of the system to the railway and assisting with preparation of the safety case. Our auditing approach is an open, exploring one using experienced staff which we believe is far more effective than a closed approach with extensive use of checklists. This conclusion is confirmed both by our clients and by those companies we have audited.
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