Rail Accident Report
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Rail Accident Report Autumn Adhesion Investigation Part 3: Review of adhesion-related incidents Autumn 2005 Report 25 (Part3)/2006 January 2007 This investigation was carried out in accordance with: l the Railway Safety Directive 2004/49/EC; l the Railways and Transport Safety Act 2003; and l the Railways (Accident Investigation and Reporting) Regulations 2005. © Crown copyright 2007 You may re-use this document/publication (not including departmental or agency logos) free of charge in any format or medium. You must re-use it accurately and not in a misleading context. The material must be acknowledged as Crown copyright and you must give the title of the source publication. Where we have identified any third party copyright material you will need to obtain permission from the copyright holders concerned. This document/publication is also available at www.raib.gov.uk. Any enquiries about this publication should be sent to: RAIB Email: [email protected] The Wharf Telephone: 01332 253300 Stores Road Fax: 01332 253301 Derby UK Website: www.raib.gov.uk DE21 4BA This report is published by the Rail Accident Investigation Branch, Department for Transport. Review of adhesion-related incidents during Autumn 2005 Contents Introduction 5 Summary 7 Key facts about adhesion performances during autumn 2005 7 Risk from adhesion-related incidents 7 Immediate causes, contributory factors and issues of concern 8 Recommendations 9 The Issue 10 Low adhesion incidents in autum 10 The parties involved 11 Location of adhesion-related problems 11 Factors that can affect adhesion 11 Management of low adhesion 12 Characteristics of low adhesion incidents 15 Response to low adhesion incidents 17 The Investigation 19 Investigation process 19 Sources of evidence 19 Key evidence 20 Analysis 21 Review of data 21 Assessment of causal and contributory factors 34 Other factors for consideration 62 Rail Accident Investigation Branch 3 Report 25 (Part3)/2006 www.raib.gov.uk January 2007 Conclusions 65 Actions already taken or in progress 68 Recommendations 70 Appendices 76 Appendix A: Glossary of abbreviations and acronyms 76 Appendix B: Glossary of terms 77 Appendix C: Key standards at the current time 80 Appendix D: An overview of magnetic brakes 81 Appendix E: Comparision between recommendations in AWG and RAIB investigations into low adhesion events during Autumn 2005 83 Rail Accident Investigation Branch Report 25 (Part3)/2006 www.raib.gov.uk January 2007 Introduction 1 The sole purpose of a Rail Accident Investigation Branch (RAIB) investigation is to prevent future accidents and incidents and improve railway safety. 2 The RAIB does not establish blame, liability or carry out prosecutions. 3 This report contains the findings of the RAIB investigation into the causes of adhesion related station overrun and Signal Passed At Danger (SPAD) incidents during autumn 2005. 4 The investigation examined: l data on adhesion performance for the years 2000, 2004 and 2005; l relevant Railway Group Standards (RGS); l data from specific adhesion-related incidents; l research on adhesion-related subjects from the UK and abroad; l other information on adhesion-related issues supplied by the parties identified below. 5 For the purposes of this investigation, access was freely given by the following organisations to their staff, data and records: l Network Rail; l Train Operating Companies (South Eastern Trains, Southern Railway, South West Trains (SWT), c2c, Merseyrail and First ScotRail); l Rail Safety and Standards Board (RSSB), who provided information from their research programme and data on adhesion-related incidents; l train owners (Angel Trains, HSBC and Porterbrook); l train manufacturers (Bombardier and Siemens); l train equipment manufacturers (Knorr Bremse); l AEA Technology who provide services to the railway industry in evaluating the performance of rolling stock; l Interfleet in their role as aVehicle Acceptance Body (VAB). 6 In addition, RAIB has consulted and exchanged information with the Adhesion Working Group (AWG), a cross-industry body that has also been investigating the causes of adhesion-related incidents in autumn 2005. The AWG has prepared a report, which was reviewed by RAIB during the course of its own investigation. Train services in Kent are now operated by ‘Southeastern’, the successor organisation to South Eastern Trains. As the latter operated services during Autumn 2005 and were consulted by the RAIB during the course of this investigation this report makes reference to South Eastern Trains where appropriate. Rail Accident Investigation Branch 5 Report 25 (Part3)/2006 www.raib.gov.uk January 2007 7 Appendices at the rear of this report contain: l a glossary of acronyms and abbreviations (Appendix A); l explanation of certain technical terms (shown in italics the first time they appear within the body of this report) (Appendix B); l a list of relevant RGS current in autumn 2005 (Appendix C); l an overview of magnetic brakes, which is a technology for stopping trains that is not used on main line railways in this country, but is used in other European countries (Appendix D); l a comparison between the recommendations from the investigation undertaken by the AWG into adhesion-related incidents in autumn 2005 and the recommendations from this report (Appendix E). 8 Two terms are used throughout this report, ‘wheelslide’, and ‘slip’: l Wheelslide refers to problems experienced by trains during braking, when wheel rotational speed is slower than the actual speed of the train. The extent of wheelslide can vary from 1-2% (wheels rotating at a slightly lower speed than the train’s actual speed) through to 100% (wheels locked when train is moving). The converse issue during acceleration, when low adhesion can cause wheel rotational speed to be higher than actual train speed is referred to as ‘wheelspin’. This report is only concerned with adhesion problems during braking. l Slip refers to the parameters within which a wheelslide prevention (WSP) system permits train wheels to rotate below the real speed of the train (extent of slip). WSP systems are provided on trains to limit the extent of wheelslide and wheelspin by modulating braking or tractive effort. In braking, most modern WSP systems permit slip values up to a maximum of 20% of real speed before intervening to release brakes and allow wheel rotational speed to build up towards the real speed of the train. 9 Reference is also made in the report to levels of adhesion between wheel and rail. This is normally expressed as a coefficient of friction (symbol µ). The lower the value of µ, the lower the adhesion between wheel and rail. Typical values for µ for dry rail would be at least 0.20. In wet weather, this can fall to 0.10. Under severe low adhesion conditions, the value of µ can drop below 0.03. As trains rely on the coefficient of friction between wheel and rail to stop, the level of adhesion available is critical to the rate at which the train can decelerate. Many modern trains have four or five fixed braking rates available to the driver, the lowest of which will normally achieve a deceleration rate of 0.3m/s2 and the highest a rate of at least 1.2m/s2. Although the relationship is not exact, a braking rate of 0.3m/s2 can only be achieved if the value of µ is at least 0.03. The value of µ would need to be at least 0.12 to achieve an emergency braking rate of 1.2m/s2. Rail Accident Investigation Branch 6 Report 25 (Part3)/2006 www.raib.gov.uk January 2007 Summary of the report Key facts about adhesion performance during autumn 2005 10 The immediate cause of the SPAD incidents that occurred at Esher on 25 November 2005 and Lewes on 30 November 2005 (which are the subject of Parts 1 and 2 of this investigation report) was poor adhesion between wheel and rail. Both trains involved had failed to stop within normally expected distances, despite the systems on the train performing in accordance with their specifications and the drivers correctly implementing the professional driving policy prevailing within the relevant Train Operating Company (TOC) at the time. Both trains had travelled a distance of approximately 3km from the time that the driver had first applied the brake. Stopping distances under normal circumstances would have been less than 2km. 11 These two incidents occurred against a backdrop of an increase in the number of adhesion- related SPAD incidents and a significant increase in the number of adhesion-related station overrun incidents on the national rail network during autumn 2005, as compared with autumn 2004: AUTUMN 200 AUTUMN 2005 Adhesion-related SPADs 7 Adhesion-related station overruns 152 30 Figure 1: Adhesion-related SPAD and station overrun incidents - autumn 2004 and autumn 2005. 12 The purpose of this investigation has been to establish the causes of this increase in adhesion-related incidents in autumn 2005 and by so doing, identify ways in which short, medium and long-term performance can be improved. Risk from adhesion-related incidents 13 When viewed from a historical perspective, the risk from adhesion-related incidents can be characterised as high in frequency but low in consequence. There have been very few accidents arising from low adhesion. The most significant adhesion-related accident occurred in November 1985, when two trains collided at Copyhold Junction in Sussex resulting in 40 people being injured, 11 of them seriously. Another low-adhesion accident occurred in November 1994 when a train ran into the buffer stops at Slough, causing the driver serious injuries. 14 However, the two near-miss incidents at Esher and Lewes in autumn 2005 demonstrate that the potential exists for a serious accident to result from low adhesion conditions. There were 6 incidents (including the Esher SPAD) where the length of the overrun exceeded 1000 metres and 18 incidents where the overrun was so severe that the driver continued to the next station rather than returning to the station that had been passed.