The Rail Accident Investigation Branch (RAIB) has called for Network Rail expedite a project intended to identify all drainage assets as part of its investigation into a train crash following a landslip near Watford last year.
The incident occurred on 16 September 2016 when a London-bound train struck a landslip at the entrance to Watford slow lines tunnel causing a derailment, which led to it being struck by a train exiting the tunnel. The driver of the train exiting the tunnel was warned of the derailment and had started to apply the brakes, reducing the impact which damaged both trains but there were no serious injuries to passengers or crew.
RAIB has said that Network Rail’s failure to investigate a previous landslide and incorporate drainage into current slope stabilisation work contributed to a failure contributed to the incident.
In addition to the drainage asset mapping, RAIB has made three other recommendations to Network Rail relating to the improvement of drainage, improvement in the identification of locations vulnerable to washout and access by the emergency services.
According to RAIB, the landslip occurred during a period of exceptionally wet weather and the location had not been identified as being at risk of a flooding-induced landslide. However, records show that a landslip occurring in the same location in 1940 also caused a derailment and drawings related to the repairs were held in a Network Rail archive. Nonetheless, these drawings were not available to either Network Rail’s asset management team or the designers of a slope protection project which was ongoing at this location at the time of the accident. As a consequence, this project made no provision for drainage.
RAIB chief inspector of rail accidents Simon French said: “The collision of a passenger train with a derailed train in Watford tunnel on the morning of 16 September last year serves as a reminder of why everyone in the railway industry continues to work so hard to manage risk - the collision of two trains in a tunnel is a scenario we all hoped never to witness.
“The landslip that caused the derailment occurred at a location that had not been identified as being at high risk (the previous landslip event at this location had occurred during the Second World War). Extreme weather events may cause earthwork failures anywhere on the network, and existing methods of assessing risk may never be a totally reliable method of predicting when and where they will occur. This leads me to conclude that more needs be done to ensure that the fundamental cause of so many earthwork failures, poor drainage, is properly addressed.”