RAIB release report into Mitcham Junction derailment

Following an investigation the Rail Accident Investigation Branch have reached a conclusion that the derailment of London CR4000 2544 at Mitcham Junction on 29th December 2014 was due to a fault in the points where the line goes from single to double track. Rather than produce a full report with major recommendations on how to prevent future similar incidents only a bulletin has been produced.

2544 departed Mitcham Junction stop just before midnight on 29th December 2014 heading towards Wimbledon with 20 passengers on board and as it approached the points where the short single track section ends was brought to a standstill as the indicator showed that they were set incorrectly. After discussions with the control room – who had been aware of the issue following the passing of the previous eastbound tram – the driver attempted to move the points to the correct position but in trying to do so he discovered that he could only get them just past the centre position. The driver then used the points bar to force the switches over and this seemed to be successful as the indicator showed they were now in the correct position. The tram was moved slowly over the points but whilst the leading bogie passed over the points correctly the switches moved between the leading and centre bogies. The centre bogie became derailed and then as the rear bogies passed over the switches – which again moved – this too was derailed. The driver stopped the tram and after checking there were no injuries amongst the passengers informed the control room and led the passengers back to Mitcham Junction stop.

The RAIB investigation examined the points and discovered that there was an obstruction which prevented the switches from moving fully across. This was found to be the damper and it appeared that the damper fluid was heavily contaminated with evidence of small sold particles within this fluid. The entire mechanism was replaced and the faulty damper was sent away for independent investigation which found that the “damper had become stuck in the middle position due to particle contamination and/or frozen water within the damper’s hydraulic circuit”.

As a full report has not been released no recommendations are made for future operation but two “learning points” are given:

• It is important that tram drivers and tramway controllers are aware of how spring operated points work.

• UK tram operators need to be aware of the findings of the consultant’s report on the condition of the points mechanism damper and consider whether any changes are necessary to their maintenance regimes.

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