ABSTRACT
Maintenance of the Safety Case What Happens to Safety Cases? There are generally two scenarios for safety cases – they are either used or they are not. When a safety case is not used, the safety case argument will remain valid for a short while – perhaps a year or so, but then critical staff will have turned over, new products or procedures will be brought into the system, the product or equipment will be used in a different way, or there may even have been a serious incident which was not originally envisaged. Eventually, the real system will have diverged so far from that represented by the safety case that the safety case is no longer valid or useful. The lack of an appropriate safety case, hazard analysis or risk assessment is regularly used in legal prosecutions as demonstration of negligence. This is absolutely correct, as having out of date information is actually worse than not having any information at all. With nothing to rely on, there is a belief that things are ‘risky’, if all the risk analysis was done a few years ago there is a belief that nothing has changed so the safety case still applies. This is extremely unlikely, there will usually have been multiple minor modifications and changes, which on their own may appear insignificant, but together could add up to a major step-change in operational use. There are several areas, which deserve special attention where change can catch out the best of safety cases: ALARP arguments, operational use and improvement, legislation shift and mishap occurrence in a related field. Each of these will now be considered in turn, although there is no priority implied by the order. ALARP Arguments If the safety case is predicated on an argument based on risk exposure being As Low As Reasonably Practicable (ALARP), a judgement will have been made about two things – the risk profile exhibited by the system and, the resources of time, trouble and expense in reducing that risk further. Over time, the perception of both areas can change, the risk profile might be viewed with more dread by the public as more research information is published; the time, trouble and expense factors may change with technological development. What was once thought expensively prohibitive (e.g. use of multiple remote control robots to sense for poisonous atmospheres), might become significantly cheaper over time. The development of new ceramics and polymers may provide improved personal protective equipment, so that certain tasks become more possible from a risk perspective.
