On 13 January 2007 at 12.23pm, an eight-car Southern train travelling from Bognor Regis to London Victoria emerged from Merstham tunnel and ran into landslip debris on the track, which derailed its leading wheelset. The driver saw the debris and applied the emergency brake to slow the train, which stopped after 320 metres. None of the 413 passengers were injured but some needed assistance to reach the public highway. The first coach received substantial damage and some signalling equipment and track bonds required replacement.
The immediate cause of the derailment was that two timber beams from a wall intended to prevent rock and soil spills had been displaced by a six-tonne root ball falling from the cutting side. There were three causal factors and four contributory factors related to the incident. The underlying cause was the lack of guidance in standards regarding root balls, and a backlog of earthworks examinations.
RAIB has made seven recommendations as a result of this incident. These involve:
- management of earthworks and vegetation
- risks from root balls
- two specific measures for Hooley cutting
- guidance for emergency services on accessing the railway and evacuating trains.
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.