02 Nov 2021
The following statement was given this afternoon by Andrew Hall, Deputy Chief Inspector, Rail Accident Investigation Branch.
"A team of RAIB inspectors arrived on site on Sunday evening and were joined yesterday by additional inspectors and our support team. We are working alongside partner organisations including the Office of Rail and Road (ORR) and BTP. Our investigation is progressing well.
"Yesterday our focus was on evidence retrieval, we have been working with Police scene officers to examine the train. We have also undertaken a close examination of the track and signalling in the area and started to talk to those involved. Analysis of downloads from the trains’ data recorders, electronic data from the signalling system and CCTV imagery is ongoing.
"From the initial evidence we have collected, we know that that the passage of the Great Western train travelling from Eastleigh across Salisbury Tunnel Junction was being protected by a red signal. At this junction, trains coming from Eastleigh merge with those from Basingstoke, so the South Western service coming from Basingstoke was required to stop at that signal.
"Unfortunately, it did not stop and struck the side of the Great Western train at an angle such that both trains derailed and ran alongside each other into the tunnel just beyond the junction.
"Initial evidence indicates that the South Western train driver applied the brakes as it approached the junction and the red signal, but the train was unable to stop before passing the signal.
"This evidence suggests that the most likely cause of this was wheelslide, almost certainly a result of low adhesion between the wheels and the track. We are continuing to pursue this as a line of investigation amongst others.
"In consultation with other parties, we continue to work with the railway recovery engineers to ensure that the site is handed back in the shortest time possible. We intend to begin releasing parts of the site back to Network Rail later today.
"Later this week we’ll be releasing the initial findings of the investigation, these will be publicly available on our website."
Head of External Communications Air, Marine and Rail Accident Investigation Branches
Accident Investigation Branches (AIBs)
The sole purpose of RAIB investigations is to prevent future accidents and incidents and improve railway safety. RAIB does not establish blame, liability or carry out prosecutions.
RAIB operates, as far as possible, in an open and transparent manner. While our investigations are completely independent of the railway industry, we do maintain close liaison with railway companies and if we discover matters that may affect the safety of the railway, we make sure that information about them is circulated to the right people as soon as possible, and certainly long before publication of our final report.