The first damaged carriages will be removed from the scene of the Salisbury train crash on Thursday.
British Transport Police said two carriages would be recovered on Thursday afternoon, with two more taken away on Friday morning.
They will be lifted from the track by a large crane.
The crash happened at 6.45pm on Sunday night as two trains approached Salisbury's Fisherton Tunnel.
Investigators believe a South Western Railway (SWR) train failed to stop at a red signal due to its wheels slipping on the rails.
The Rail Accident Investigation Branch said this led to it travelling 220 metres past the signal before smashing into the side of a Great Western Railway train at the point where the tracks they were on merged.
Both trains derailed and travelled into the tunnel before coming to a standstill.
The SWR train was driven by Robin Tandy, 74, who suffered what police described as "life-changing injuries".
Thirteen passengers were treated in hospital for minor injuries.
Disruption to services through Salisbury is expected to continue until at least the end of next week.