Poor training and driver fatigue may have contributed to a London Underground train travelling with some of its doors wide open, a report found.
The Jubilee Line service had about 30 passengers on board as it moved at 39.5mph (62kmh) between Finchley Road and West Hampstead on 1 September.
The Rail Accident Investigation Branch (RAIB) said the driver did not see some doors had not closed after a fault.
Transport for London (TfL) has been contacted for comment.
Footage was tweeted from a train where 10 doors were open as it travelled for 56 seconds at full speed between the two stations at about 09:00 BST, but no-one was injured as a result.
The RAIB report into events found when the train stopped at Finchley Road some doors “opened without being commanded to do so by the train operator”.
‘Sudden workload increase’
He was unable to open or close any doors, so operated a switch to bypass the door locking circuit intended to prevent the train departing with doors open.
“He then did not notice that some doors remained open when departing,” the report said.
The investigation found his actions were “probably influenced” by a sudden increase in his workload from the low-level associated with automatic train operation, fatigue from his sleeping pattern, and/or low blood-sugar levels from a prolonged period without food.
It added a possible factor was training did not “adequately prepare” drivers to manage the sudden increase in workloads caused by faults.
The RAIB has made four recommendations to London Underground, including improvements to Jubilee line trains, better training for drivers and the raising of awareness on “safety from insufficient sleep and inappropriate eating patterns”.