Trains are expected to start running again on the Cambrian line between Machynlleth and Shrewsbury on Monday.
Buses have been replacing trains since last Monday, when two Transport for Wales trains collided head-on near Talerddig passing loop.
One man died and fifteen other passengers were injured, four of them seriously, when a westbound train overran the loop and collided with an eastbound train. It has been reported that the man who lost his life had suffered a heart attack.
Initial investigations by the Rail Accident Investigation Branch have revealed that rail adhesion was ‘relatively low’, leading to speculation that the down train could not be stopped in the loop but slid beyond it.
It has also been reported that the driver of the train left the cab in the last few seconds, and warned passengers to brace themselves because a collision was imminent.
Network Rail has been working to separate and remove the damaged trains.
Simultaneously, Network Rail engineers have been carrying out repairs, maintenance and safety inspections.
Test trains will run through the area to make sure everything is operating normally before passenger services restart on Monday, but Network Rail has warned there could still be some disruption for a while.
Network Rail’s Wales & Borders route director Nick Millington said: ‘Monday night’s tragic events will forever be etched in my memory and my thoughts remain with all those affected. Thankfully, incidents like this are extremely rare on the railway network. We continue to operate one of the safest railway networks in Europe.
‘Our engineers have been on site throughout and have conducted very thorough safety checks and we will run test trains through the area.
‘I am grateful to the local community who have been very accommodating throughout this last week while we have been managing this incident.
‘I would also like to thank passengers for their patience, understanding and support during the last few days as our teams have worked tirelessly to restore the railway as quickly as they could.’
TfW chief operating officer Jan Chaudhry van der Velde added: ‘The railways in Wales have a very good safety record, so when serious incidents like this happen, we at TfW, together with our partners at Network Rail, are determined to get to the bottom of what caused it. For that reason, we are co-operating fully with the authorities investigating the collision, and in particular, the Rail Accident Investigation Branch.
‘Our condolences go to the family of the passenger who passed away, and we hope that those passengers and staff members injured in the collision make a speedy recovery.’