CCTV, track irregularity, hot weather – a look at what this report sayspublished at 13:09 BST
13:09 BST
Katy Austin
Transport correspondent
Investigators say CCTV from the train which derailed near Lewes last week, and other trains that used the line on the same day, show there was an “irregularity” with the track geometry just before the point where the train came off the tracks.
The Rail Accident Investigation Branch said it had received “several reports of rough riding at the location of the derailment from passengers on other trains”. Its initial update also highlights that the accident took place during a sustained period of hot and dry weather.
It says the clay embankment and the material underneath it are sensitive to changes in moisture content, and may move as moisture levels change.
The RAIB says there is evidence that some movement had previously taken place, but no evidence to indicate a significant slip before the accident.
The rest of the investigation will now consider elements including:
how that section of track was inspected and maintained
the condition and maintenance of the embankment
the weather conditions and how effective any hot weather mitigation measures were – intended to address the risks of operating trains in hot weather
The train was travelling at around 65mph as it approached the point of derailment, within the 70mph speed limit. Three carriages of the train from London Victoria to Eastbourne came off the tracks on Thursday afternoon.
They ended up on their side down an embankment. Twenty people needed hospital treatment, with two seriously injured.
The RAIB has today released its initial update and its full investigation is continuing.