On Monday 29 May a locomotive-hauled passenger train was travelling from Dalegarth to Ravenglass when the leading bogie of the sixth coach derailed at Spout House Curve. On Wednesday 5 July, the leading bogie of the fifth coach of a different locomotive-hauled passenger train derailed at Millwood Bank. There were no injuries or significant damage to the track in either incident.
The immediate cause of the Spout House Curve derailment was flange climb of the leading right wheel, due to the combination of a vehicle fault and the track condition. There were two causal, several contributory and one underlying factor to the derailment.
The immediate cause of the Millwood Bank derailment was flange climb of the leading right wheel, due to a combination of vehicle, track and operational factors, which resulted in an excessive amount of vehicle sway and wheel unloading. There were three causal, three contributory and one underlying factor to the derailment.
RAIB has made eight recommendations as a result of its investigation these include:
- a fleet check of axlebox clearances and its inclusion in ongoing maintenance practice;
- development and implementation of a vehicle maintenance regime which is based on the assessment of hazards identified from both past experience and analysis of possible future failure modes;
- review of the suspension set up on the type of bogie involved in the derailment at Millwood Bank, to ensure it is consistent with the track condition;
- examination of the track to identify current and likely future areas of poor condition and remedial work where necessary, particularly with regard to voiding below sleepers;
- review of the existing track fault reporting system and the reaction to reported faults and mandating of the system;
- implementation of a system to identify track faults liable to cause excessive sway and when mitigation measures should be triggered;
- briefing of operational staff on the signs of and risk from excessive vehicle sway.
Response to recommendations:
- RAIB will periodically update the status of recommendations as reported to us by the relevant safety authority or public body.
- RAIB may add comment, particularly if we have concerns regarding these responses.