A passenger was seriously injured when her bag got caught in a train door, dragging her along the platform and on to the track, according to a new report into accidents.
The train driver did not spot the woman on CCTV cameras and pulled away, dragging her along, before she fell under the train at West Wickham station, south London, in April 2015.
Train operator Southeastern said offered support to the woman after the "terrible incident" in April 2015.
The train was driver-only operated, which means drivers are required to check platform CCTV monitors to ensure it is safe to depart stations.
It was being driven by a trainee driver under the supervision of an instructor but neither was aware that the passenger was stuck," the RAIB stated. Investigators were not able to establish why this was the case.
The report was published by the Rail Accident Investigation Branch (RAIB).
Tests showed that this could only occur if a passenger pressed the door-open button within a second of the driver initiating the door closure sequence.
The RAIB recommended that train operators and owners correct all door control systems which exhibit "the unsafe characteristics" found in this incident, and that guidance to staff dispatching trains is changed so they watch the doors while they are closing in addition to after they close.
A separate investigation into an incident involving a passenger being dragged along an Underground platform after getting her coat caught in a Tube train door is being carried out.
The woman ended up falling between the gap between two carriages of the Northern line train and was taken to hospital with serious arm and head injuries.
The incident at Clapham South station in south London happened on March 12 last year.