This study investigates the risk assessment of railway changes in an interconnected environment. Systems are a collection of subsystems and parts, and this thesis develops a new method, the Combined Assessment Method (CAM), to analyse them. CAM potentially applies to many industries, including aviation, defence and nuclear, where there is a requirement to assess system safety objectively. The railway is a specific case of a closely coupled socio-technical system of critical physical interfaces between systems and a stringent example of systems in other industries.
The Author has carried out: an assessment of current techniques, a review of relevant literature, a survey of risk assessment practitioners, an appraisal of current methods, and a review of accident data to identify current accident characteristics.
CAM incorporates established assessment techniques to perform subsystem analysis. Subsystem results are combined using systems engineering methods in a novel way producing an overall risk assessment for a system, which incorporates emergent behaviours.
The assurance of CAM is through a case study and two test cases. It uses safety performance, ease of use, and economic saving criteria to judge success. Illustrative studies include a metro system, indicating that CAM is potentially a process and is application-independent. Furthermore, test cases illustrate that CAM combines the risks from multiple parts of a whole system into overall risks.
Finally, test cases measure the verification through a match between the findings of official incident reports and the CAM output.
This thesis is the first step to creating CAM as a fully-fledged system safety risk analysis method. Further work is proposed to take CAM forward and address identified weaknesses. Finally, suggestions have been made for further work to “productionize” CAM to increase the likelihood that practitioners in the field will use CAM
