A short history of traction safety cases

Summary form only given as follows. This presentation traces the development of the safety case based acceptance process for electric traction. Starting with the 1996 West Coast main line electrification, it shows how the exercise of pragmatic judgement by experienced engineers, who signed off new traction as safe to run on the basis of test data, has given way to highly detailed risk analysis with acceptance depending on the pragmatic judgement and experience of a small number of specialists with the expertise to sign off the safety cases of new traction on the basis of unprecedented quantities of test data. The main difference is that in the modern railway and the blame culture of society today, the signature on the acceptance certificate could be an exhibit in the court of law. Issues highlighted include the inherent conflict between an infrastructure provider and operators seeking to introduce new technology not foreseen by the designers of the existing signalling equipment. But it also points out that if modern acceptance procedures were applied retrospectively to existing trains they would probably not pass the Electrical Systems Review Panel. The need for a total safety analysis is emphasised. To illustrate the issues, samples of interference readings from modern traction are shown, drawn from test results with a number of trains. Experience with several projects is quoted. To conclude, the progress with safety cases for the current builds of Adtranz and Alstom EMUs is brought up to date