The Move to Performance Based Standards - Managing Uncertainty University of York Safety Critical Systems Engineering MSc

The regulation of safety in a range of industries is changing to support government legislation and advances in technology. Historically, safety regulations have contained a list of prescriptive requirements describing the 'means' to achieve an acceptable level of safety. More recently, there has been a tendency in the industrialised nations to shift towards performance based safety regulation whose requirements describe 'what' levels of safety must be achieved, without prescribing the 'means' by which it is to be achieved. There is a need for a clear understanding of the safety requirements to be satisfied in meeting legal obligations, especially as this shift aims to move more responsibility and ownership onto the shoulders of the service providers. This responsibility will include the presentation of a safety case to provide the safety evidence in a comprehensible and sound argument to satisfy the safety requirements of the domain regulating bodies. This shift, from the use of prescriptive based standards to a more performance-based regime, is set to provide challenges to the safety community. The alternative approaches and the motivation for change are reviewed; current thinking on the challenges ahead are also discussed and identified. It is shown that performance standards offer increased freedom and opportunities to the supplier in developing their design, which the author believes has the potential to increase uncertainty. It is further shown that the additional responsibility associated with performance-based development requires that the scope of the system safety hazards is well recognised and understood. The tools and methods used in the design and analysis must be applied and performed systematically by suitably qualified engineers so as to achieve an acceptable design, capable of meeting safety targets, tolerable to the regulator and society. The uncertainty in this process must firstly be identified and then managed effectively to progressively increase confidence for the argument strategies to be employed in support of the safety case. Uncertainty is considered through the lifecycle to identify common sources and manage them effectively. The uncertainties likely to be encountered in the development of a system safety case are identified and categorised. A checklist of these uncertainties is provided for use by the system developers, auditors and the regulator as a guide to recognising uncertainties, at each phase of the lifecycle, as they materialise and indicate how to combat such uncertainties. Any uncertainty identified during the safety lifecycle needs to be recognised and a means of reinforcing the …