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) said safety was “always our top priority”.
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. No-one was injured.
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, but left the station with some still open.
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”.
London Underground has since given all train drivers additional guidance on how to operate trains during unusual faults.
Jill Collis, TfL’s director of Health, Safety and Environment, said TfL had begun work on several of the RAIB’s recommendations following an internal report.
“We will continue to review our procedures to ensure we consider all of the recommendations made in the RAIB report, and continue to work to ensure that the Tube network is as safe as possible,” she added.