Development of risk models for generic hazards of the Jerusalem light rail transit system

Quantitative safety risk models (SRMs) for mainline railways are designed to enhance safety performance in the mainline sector. They are used to identify the safety risks most affecting railway systems by quantifying the predicted outcomes of the risks, in terms of frequency and level of seriousness. This study focusses on tramway systems operating according to line-of-sight principles. During the literature review phase of his research, the author was not able to identify a single generic safety risk model for a tramway system along the lines of the UK SRM that had been developed for the mainline railway. He also did not discover a specific safety risk model associated with a particular hazard inherent in the operation of tramway systems. However, at a later stage of writing the thesis the author came across a paper that discusses the application of a random effects negative binomial model to examine the frequency of accidents involving trams. The present study aims to quantify the risks associated with three generic tramway operation hazards, namely, excessive jerk, collisions between trams due to signals passed at danger events (SPADs) and overturning of a tram on a sharp curve due to excessive speed. The author demonstrates that SRMs can be developed for line-of-sight tram operations. The risk modelling and quantification are based on statistical models and fault tree/event tree models. SRMs for SPAD and overturning of trams on sharp curves were developed to assess the potential risk, given the limited occurrence of these hazards. Since they are considered rare events with sparse data, the model results were validated against expert judgement. The risk evaluation and acceptance were based on the criteria set by the Jerusalem Master Plant Team (JTMT) and international criteria. The findings indicate that a comprehensive SRM can be developed for the Jerusalem Light Rail Transit (JLRT) network, a system that operates accor-ding to line-of-sight tram operation, using modelling techniques developed for the mainline sector. The models developed in this study are based mainly on past accident reports from the JLRT network; they show that the existing residual risks are Undesirable and cannot be accepted and therefore additional mitigation measures must be applied. This study makes an original contribution to quantitative risk assessment by creating a practical methodology for the study of low-frequency, high-consequence events. Moreover, the results of the ri