At about 12:15 hrs on Wednesday 2 April 2014, two wagons of a nominally empty freight train derailed on the approach to Angerstein Junction, near Charlton in south east London. The derailed wagons were pulled over the junction and stopped on the Blackheath to Charlton line, with the two wagons partly obstructing the line used by trains travelling in the opposite direction. No other trains were involved in the accident and no-one was injured, but there was significant damage to the railway infrastructure.
The wagons derailed because the leading right-hand wheel on one of them was carrying insufficient load to prevent the wheel climbing up the outer rail on a curved section of track. The insufficient load was due to a combination of a track defect, an unevenly distributed residual load in the wagon, and an uneven distribution of load associated with a twisted bogie. The unevenly distributed residual load comprised finely crushed rock which adhered to the side of wagon, and was not discharged by unloading procedures. These procedures had been developed without recognising the derailment risk associated with carrying relatively small, but significantly unbalanced, loads. This combination of factors illustrates the derailment risk which arises when wagons carrying one or more defects are operated on track with one or more defects in circumstances where both wagon and track are compliant with relevant railway standards (ie the defects on wagon and track are not, individually, sufficient to prevent train operations continuing).
As a consequence of this investigation, RAIB has made six recommendations, several of which could be informed by work undertaken as part of a cross-industry programme already initiated by the ORR after previous RAIB investigations identified derailment risks associated with operation of wagons and track which are imperfect, but nevertheless compliant with relevant standards.
One recommendation addressed to Aggregate Industries seeks improved wagon load discharge arrangements. Two recommendations addressed to RSSB are intended to mitigate risks associated with imperfect wagons, carrying unevenly distributed loads, on imperfect track. Three recommendations, addressed to Network Rail, seek appropriate control of derailment risk in sidings where derailed vehicles can affect running lines, provision to wagon operators of wagon defect information collected by trackside equipment, and possible modifications to the method of collecting track twist data in order to reflect the effect of this track defect on modern rolling stock.
Notes to editors
- The sole purpose of RAIB investigations is to prevent future accidents and incidents and improve railway safety. RAIB does not establish blame, liability or carry out prosecutions.
- RAIB operates, as far as possible, in an open and transparent manner. While our investigations are completely independent of the railway industry, we do maintain close liaison with railway companies and if we discover matters that may affect the safety of the railway, we make sure that information about them is circulated to the right people as soon as possible, and certainly long before publication of our final report.
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Newsdate: 12 August 2015