Quantified risk assessment in railway system design and operation

Over the last few years quantified risk assessment (QRA), a technique developed in the process industries, has moved into the railway and mass transport arenas. Many quantified risk assessments are now appearing covering varying aspects of railway operation and design. This paper highlights the strengths and weaknesses of the QRA technique, with specific reference to its use in railway system design and operation. Suggestions are made as to how best to manage and present a QRA, and these are illustrated in a section explaining the systematic approach of Cross Rail, a joint London Underground/British Rail/Railtrack £2 billion railway for London. Throughout this paper it is stressed that good QRA comes from management of the process and not of the ‘final figure’. The paper concludes with a listing of recommendations that are considered to be the minimum needed for the future progress of railway QRAs. Consequently the paper will be of special interest to those railway organizations undertaking or managing a QRA for the first time. Special reference is made to the use of QRAs in the presentation of Railway Safety Cases and project design.