Railway Safety - Risks and Economics

University dissertation from Stockholm : Infrastruktur

Abstract: Safety analysis is a process involving several techniques.The purpose of this thesis is to test and develop methodssuitable for the safety analysis of railway risks and railwaysafety measures. Safety analysis is a process comprisingproblem identification, risk estimation, valuation of safetyand economic analysis. The main steps are described in separatechapters, each of which includes a discussion of the methodsand a review of previous research, followed by the contributionof this author. Although the safety analysis proceduredescribed can be used for analysing railway safety, it has suchgeneral foundations that it can be used wherever safety isimportant and wherever safety measures are evaluated. Itcombines cost benefit analysis with criteria for thedistribution and the absolute levels of risk.Risks are estimated with both statistical and risk analysismethods. Historical data on railway accidents are analysed andstatistical models fitted to describe trends in accident ratesand consequences. A risk analysis model is developed usingfault tree and event tree techniques, together with Monte Carlosimulation, to calculate risks for passenger train derailments.The results are compared with the statistical analysis ofhistorical data.People's valuation of safety in different contexts isanalysed, with relative values estimated in awillingness-to-pay study. A combination of focus groups andindividual questionnaires is used. Two different methods areused to estimate the value of safety and the results arecompared. Comparisons are also made with other studies.Different approaches for safety analysis and methods foreconomic analysis of safety are reviewed. Cost-benefit analysisas a decision criterion is discussed and a study on theeconomic effectsof a traffic control system is presented.There are several results of the work. Historical data showsa decrease in the accident rate. The average consequence ofeach accident has not changed over time. The risk analysismodel produces comparable results and enables analysis ofvarious safety measures. The valuation study shows that peopleprefer the prevention of small-scale accidents over theprevention of larger, catastrophic accidents. There are onlysmall differences in the valuation of safety in differentcontexts.

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