The Rail Accident Investigation Branch (RAIB) will examine the maintenance history of a “heavily worn” switch rail of points which is believed to have caused a derailment near Edinburgh Waverley last month.
The RAIB said its full investigation will review the history of the points concerned and work that was carried out on them in the days before the accident, after a preliminary investigation found that the accident occurred because the wheel flanges “climbed over” the “heavily worn” left-hand switch rail of points.
Network Rail has examined the other switch rails in the area and has not found any others in a similar condition.
The RAIB’s full investigation will also look into the competence and fitness of the maintenance staff, and the organisation and resourcing of infrastructure maintenance in the Edinburgh area.
The 3-car class 170 diesel multiple unit train was empty of passengers when it became derailed to the left at a speed of 30.5km/h on 27 July, at the junctions in Princes Street Gardens, Edinburgh.
The train ran for about 90m before coming to a stop. No people were hurt, but the derailed bogie caused damage to the track and there was some damage to the underside of the train.