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This paper describes a system for the investigation of railway interfaces that is under development within the Rail Safety and Standards Board (RSSB). Going through its preliminary stages at the time of writing, the target is to adopt this method as a formal part of the standards development and review process that RSSB manages on behalf of the mainline railway operators in GB. Although the work described...
There is an important interface between requirements and safety engineering, but its very existence causes a problem: it belongs to neither discipline. This paper looks at identifying failure modes from a requirements perspective, and considers how the two disciplines can most effectively collaborate. Requirements techniques have evolved rapidly in the last 10 years from the traditional hit-and-miss...
This paper discusses an experiment that measured the effectiveness of a hazard identification process used to support safety in Defence Standard 00-56 project. The experimental case study utilised a Ministry of Defence project that assessed simultaneously two potential suppliers who were competing for a MOD equipment contract. The UK MOD Corporate Research Programme funded the comparison work and...
In mission critical systems the operational success of the system depends on many aspects of the system's operation such as availability, security, performance and safety. According to the design of the system, dependability attributes can be in conflict or in harmony often resulting in unavoidable trade-offs. Adopting a more flexible approach towards dependability allows us to achieve tolerable limits...
This paper sets out a methodology for setting tolerable risk levels, for various methods of Safety Integrity Level (SIL) determination, to meet the principles as low as reasonably practicable (ALARP). It makes proposals on how to deal with the tolerable risk concept for safety instrumented systems (SIS) protecting against single hazards.
This paper presents some considerations related to software safety requirements in critical computer systems, particularly in the space project domain. Some requirements issues concerning systems and software engineering are discussed, from a cultural change perspective, showing the main obstacles to be overcome in the requirements elicitation activity. The intention is to contribute with the discussion...
This paper describes the process by which the safety requirements for a future motorway control system were derived. Although the problem domain was found to be amenable to standard analysis techniques, it was necessary to adapt the techniques used to allow for domain specific factors and behaviours, for example, the indirect nature of the causal link between a failure within the system boundary and...
In this paper, the question of artificial intelligence (AI) techniques usage is discussed in the light of European standards. An application of predictive fuzzy logic for a train control system is then presented and a solution for the question is employed. Some benefits like headway shortening and less energy consumption may be achieved. Finally, some conclusions taken from the application results...
This paper presents a design methodology for behaviour-based intelligent control systems, which we argue is suited to safety critical applications. The methodology has a formal basis, and uses dynamical systems theory to prove system safety properties that are expressed in terms of Lyapunov stability. We propose a new computational model for implementation of these systems, which offers a reduction...
Unmanned Aerial Vehicles (UAVs) are set to become part of every day air traffic operations perhaps within the next few years; however there are significant challenges that must be addressed in order to seamlessly introduce UAVs into non segregated airspace. This paper discusses some of the identified safety challenges in achieving this objective, taking a rigorous look at how one might argue the safety...
Swarm Intelligence provides us with a powerful new paradigm for building fully distributed de-centralised systems in which overall system functionality emerges from the interaction of individual agents with each other and with their environment. Such systems are intrinsically highly parallel and can exhibit high levels of robustness and scalability; qualities desirable in high-integrity distributed...
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