HomeGovernanceAccident InvestigationRecent ‘trap and drag’ leads RAIB to discuss limits of detection systems

Recent ‘trap and drag’ leads RAIB to discuss limits of detection systems


RAIB has cautioned against relying on door closing systems to tell if it is okay for a driver to leave the station – after a passenger had their hand stuck in the door and had to run to keep up.

The incident is by no means unique, either.

RAIB cited other incidents which had comparable issues.

At Newcastle Central station, on 5 June 2013, a passenger was dragged along the platform after their wrist became trapped in a closing door. The investigation found that the conductor had not carried out a safety check before signalling to the driver that the train could depart.

Two years later, at Hayes & Harlington station on 25 July 2015, a passenger was dragged by a train when the driver did not identify that their hand was trapped in the closed and locked doors. The investigation found that the door detection system did not detect the passenger’s hand in the closed door, and that the train driver and other train company staff believed the door interlock system would detect the presence of an object such as a hand.

Furthermore, at Bushey station on 26 March 2018, a passenger was dragged when their wrist became trapped in the closed and locked doors of a departing train. The guard incorrectly believed that the door interlock could be relied on to determine whether anyone was trapped in the closed doors.

At Elstree and Borehamwood on 7 September 2018, a dog’s lead became trapped in the closing doors of a departing train, which dragged the dog off the platform and led to its death. The investigation noted that the obstruction detection system did not detect the dog’s lead and that the driver did not observe that the dog’s owner was in close proximity to the closing doors when starting the train.

On all these occasions, a detection system missed objects – this is because if they are thinner than 30mm – so a hand, for example – or non-rigid, it will close. On some, the drivers were relying on an interlocking system (which says the door has finished its closing movement) to say it is safe to go.

Some echoes of the above were found in a recent incident at Wood Street station.

The train involved in the incident, reporting number 2T25, was the 08:14 hrs Arriva Rail London (ARL) service from Chingford to London Liverpool Street. It was formed of two class 710 Aventra electric multiple units, each of four cars. Passengers cannot pass between the front and rear four-car units without leaving the train.

RAIB said this incident occurred because the driver did not appreciate that the passenger was in an unsafe position when he made the decision that it was safe to start the train. The driver stated that, although he had seen that the passenger was close to the side of the train before starting off, he was unaware that she was trapped in the doors and believed that she was pressing the ‘door open’ button to try and board the train.

The door interlock system, meanwhile, had said the doors were closed. A train cannot depart if that is not the case.

The doors and interlock system of the train involved were tested after the incident and were found to comply with the applicable ARL standards.

ARL requires drivers should observe the dispatch corridor (the area consisting of the platform immediately alongside the train, the gap between the platform and the train and the full height of the doors) during the dispatch process, and reminds drivers of the importance of the train safety check, stating ‘When the door interlock light is illuminated… check once more that the dispatch corridor is clear, that nothing is trapped in the door, the platform edge and gap appear clear and it is safe for the train to depart.’

RAIB added the driver later stated that he did not believe that the passenger could have been trapped in the doors when he started the train, because he had obtained a door interlock. This suggests that the driver was, in these circumstances, using the interlock to indicate whether it was safe to start the train.

Research by RSSB (T1102 ‘Optimising door closure arrangements to improve boarding and alighting’, 2017) has shown that some passengers believe train doors that are closing can be reopened like lift doors, by placing a hand between them. However, as this incident shows, a hand placed in the doors may not always activate obstacle detection systems or prevent door interlock circuits from being completed.


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