Investigators discover pre-existing track defect

The Rail Accident Investigation Branch (RAIB) has revealed that a track defect existed at the site of the recent train derailment near Lewes, East Sussex, before the accident occurred. The incident on August 13 left around 30 people injured, with two people suffering serious but not life-threatening injuries.

The RAIB's preliminary findings, released this week, state that CCTV images from trains using the line earlier that day showed a "track geometry irregularity" on the immediate approach to the point of derailment. Investigators also reported receiving several accounts of "rough riding" from passengers on other trains at the same location before the crash.

The disclosure was made as part of an ongoing investigation into the derailment of the 14:24 Southern service from London Victoria to Eastbourne, which left three carriages tipped on their sides down an embankment.

Weather and embankment under scrutiny

The accident occurred at about 15:44 BST, shortly after the UK had experienced its hottest day of the year so far, with temperatures reaching 38.1C in west London. The RAIB noted that the incident took place during "a sustained period of hot and dry weather," with temperatures as high as 33C registered shortly before the derailment.

The embankment at the site is made of clay and alluvium, materials that are sensitive to changes in moisture content and may move as moisture levels change. The RAIB said there is no evidence of a significant embankment slip before the accident, but there is evidence that some movement had previously taken place.

Investigators said the derailed train was travelling at about 65mph, within the 70mph speed limit, and the driver had begun to brake as it approached the point of derailment. The train was an eight-carriage service carrying approximately 150 passengers.

Investigation to examine maintenance and mitigation

The RAIB said its investigation will consider how the section of track was inspected and maintained, the condition and maintenance of the embankment, the weather conditions, and the effectiveness of measures taken to address issues caused by hot weather. The branch has recovered data from the front of the train's "black box" and will obtain data from other recorders during recovery operations. CCTV recordings, signalling data and radio communications have also been obtained, and the train, track and embankment have been surveyed using laser scanning and aerial photography.

Injuries and emergency response

Two people were taken to a major trauma centre with "severe" injuries, according to deputy chief paramedic officer Michael Bradfield, who said there was a "range of injuries" among the 20 people taken to hospital. Eighteen others were treated for less serious injuries and have since been discharged. Ian Drummond-Smith from the British Transport Police said a "major incident" had been declared, but all passengers had been "safely evacuated."

Passengers described the terrifying moments as the train left the tracks. Rachel Heath said it felt like the train "had been lifted into the air," while Tracy McGregor said she took the brace position and was "preparing to die." Yana Ludwig described the experience as "completely terrifying," saying there was a banging and "everything just went topsy-turvy" before the carriage fell on its side. Rob Bradley said his carriage "jumped upwards" and the train skidded for a while before stopping.

Line closure and removal challenges

The railway line between Lewes and Haywards Heath has been closed since the incident, with disruption expected to continue until at least August 26. Network Rail and Southern Rail said the carriages will need to be lifted away by crane, a task complicated by the location near a river, within a site of special scientific interest, and with restricted road access.

Official responses

Lucy McAuliffe, Network Rail's route director for Sussex, and John Whitehurst, chief executive of Greater Thameslink Railway, issued a joint statement apologising for the derailment and saying they are "fully committed to supporting the current investigation." They said they will "carefully consider any recommendations arising from the investigation and work across the industry to implement them."

The Department for Transport said in a statement that "the UK's railways remain among the safest in the world," noting that delays caused by track faults have fallen by 45% since the late 2000s. The department also highlighted its investment of £29bn to renew and maintain the network, with an additional £2.6bn to improve climate resilience.

Network Rail's group safety and engineering director Martin Frobisher told the BBC that speed restrictions were not in place along the section of track when the derailment happened, and insisted the railway was safe.