Phipps Bridge on Croydon Tramlink 25 May 2006
Total Page：16
File Type：pdf, Size：1020Kb
Rail Accident Report Derailment at Phipps Bridge on Croydon Tramlink 25 May 2006 Report 28/2007 August 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. Derailment at Phipps Bridge on Croydon Tramlink, 25 May 2006 Contents Introduction 4 Summary of the report 5 Key facts 5 Conclusions 6 Recommendations 6 The Accident 7 Summary of the events 7 Previous occurrences of a similar character 7 The parties involved 7 Location 8 Infrastructure 8 The tram 10 Events preceding the accident 10 Events during the accident 12 Events immediately following the accident 12 The Investigation 14 Investigation process 14 Analysis 14 Conclusions 19 Actions reported as already taken or in progress relevant to this report 20 Additional observations 21 Recommendations 22 Appendices 23 Appendix A: Glossary of abbreviations and acronyms 23 Appendix B: Glossary of terms 24 Rail Accident Investigation Branch Report 28/2007 www.raib.gov.uk August 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 Access was given by Tramtrack Croydon Ltd and Tram Operations Ltd to their staff, data and records for the purpose of this investigation. 4 Appendices at the rear of this report contain Glossaries: l acronyms and abbreviations are explained in the glossary at Appendix A; and l certain technical terms (shown in italics the first time they appear in the report) are explained in the glossary at Appendix B Rail Accident Investigation Branch Report 28/2007 www.raib.gov.uk August 2007 Summary of the report Key facts 5 Tram number 2532, a 3-section articulated unit, travelling eastbound on the single line between Wimbledon and Croydon with approximately 180 passengers on board, became derailed after passing over facing points PBR02G at the single to double line junction on the approach to Phipps Bridge tram stop near Merton, Surrey, at 15:57 hrs on Thursday 25 May 2006. As the tram approached the points they were set, incorrectly, in the reverse position. After the leading bogie of the tram had passed over, the points sprang back to the normal position and the centre and rear bogies of the tram took that route. As the paths taken by the front and rear of the tram diverged, the centre bogie became derailed. The tram came to rest about 43 m beyond the points (Figure 2). Location of accident © Copyright TfL Reg. User No. 06/E/1692 Figure 1: Extract from TfL map showing diagram of Croydon Tramlink system and location of accident 6 There were no injuries, and the passengers were evacuated to the adjacent tram stop by the driver and other staff. Recovery of the tram was completed at 21:40 hrs and normal services were reinstated at 22:10 hrs the same day. 7 A derailment occurred at the same location in very similar circumstances on 21 October 2005. A report of the RAIB investigation into that incident was published on 29 March 2006. Rail Accident Investigation Branch Report 28/2007 www.raib.gov.uk August 2007 Conclusions 8 The immediate cause of the accident was that the tram driver did not react to the ‘points not correctly set’ indication on the points position indicator (PPI) sited 4 m on the approach to points PBR02G at Phipps Bridge, and did not stop the tram before reaching the points. 9 Causal factors were: l the points did not return to normal after the passage of the previous tram, and the vibration of the tram passing over the points caused them to spring back to the normal position under the tram. l the poor conspicuity of the indicator display when the points are not set correctly. 10 In addition, the following factors were considered to be contributory: l the control room staff were not able to alert the tram driver in time to the malfunction of the points. l the unreliability of this set of points, which was the subject of recommendation 2 from the report into the derailment on 21 October 2005, and which had not been remedied. l the recommendations from RAIB’s report into the derailment of 21 October 2005 (published on 29 March 2006) relating to: a. the conspicuity of the PPI indication; and b. the reduction of the number of alarm messages received by the control room staff had not been implemented. l the absence of a systematic approach to investigating and rectifying faults in the points mechanism at Phipps Bridge. Recommendations 11 Recommendations can be found in paragraph 85. They relate to the following issues: l Implementation of the recommendations from the report into the derailment of 21 October 2005 (see paragraph 10 above). l Further work to improve the response of the infrastructure controller to recurrent faults. Rail Accident Investigation Branch 6 Report 28/2007 www.raib.gov.uk August 2007 The Accident Summary of the events 12 At 15:57 hrs on Thursday 25 May 2006, tram 2532 approached Phipps Bridge tram stop on its journey from Wimbledon to Elmers End (Figure 1). The PPI for facing points PBR02G was displaying a single white dot, indicating that the points were not correctly set for the normal route (to the left, in the direction the tram was travelling). The tram driver did not react to this indication, and drove the tram over the points. The points were set, incorrectly, to reverse (for the right-hand route). The leading bogie of the tram followed this route. As the tram passed over the points they sprang back to normal, and the centre bogie of the tram followed the route to the left. The leading wheels of the centre bogie became derailed and the tram stopped abruptly after travelling 43 m past the points, about 50 m before the tram stop platform. 13 There were about 180 passengers on board the tram. There were no injuries to staff or passengers. 14 The tram was re-railed at 21:40 hrs and normal services resumed at 22:10 hrs. Previous occurrences of a similar character 15 A derailment in very similar circumstances occurred at the same place on 21 October 2005, and was the subject of an RAIB investigation, the report on which (number 04/2006) was published on 29 March 2006. This report concluded that the derailment occurred because the tram driver did not react to the ‘points not correctly set’ indication. Four recommendations were made, which are discussed at paragraphs 60 - 69. There had been a previous derailment on spring facing points at Mitcham in August 2002. This was caused by a wrongly adjusted points mechanism, and subsequently all the points mechanisms on the Tramlink system were checked and adjusted as necessary. The parties involved 16 The Croydon Tramlink system, which opened in 2000, is run under contract by Tramtrack Croydon Ltd (TCL), which has a 99-year concession from Transport for London (TfL) to provide a service. The system is operated under contract to TCL by First Tram Operations Ltd (TOL), which employs the tram drivers and controllers, and the trams are maintained by Bombardier Transportation Ltd. Maintenance of the infrastructure is contracted by TCL to Mowlems (now part of Carillion plc). Rail Accident Investigation Branch 7 Report 28/2007 www.raib.gov.uk August 2007 Location 17 The Wimbledon to Croydon line of the Tramlink system runs in a generally north west – south east direction throughout its 10 km length. It is double track from a short distance outside Wimbledon station for 2.13 km as far as Morden Road, where the line becomes single for 0.72 km. Double line resumes at points PBR02G, which are located some 90 m before reaching Phipps Bridge tram stop (Figure 2). Direction Points Position Indicator of travel Phipps Bridge Tramstop Points PBR02G Tram 2532 after derailment FROM WIMBLEDON TO CROYDON 0 6 10 20 N Scale (metres) Figure 2: Site plan Infrastructure 18 In common with all of the single/double line junctions on the Tramlink system, PBR02G points at Phipps Bridge are equipped with a Hanning & Kahl HW160 type mechanism, arranged to operate as spring points. An outline description of the points mechanism was given in the previous report. In view of the connection between the problems with the points mechanism and the derailments at Phipps Bridge, a more detailed account is given below. 19 The Hanning & Kahl mechanism in use at Phipps Bridge is deemed by the manufacturer to be suitable for use with flatbottom section switch rails. The off-street turnouts on the Croydon Tramlink system use rail of this type, with shallow-depth switch rails and S49 section running rails.