A Southern train on the way from Tattenham Corner to London Bridge travelled for a brief period with its doors open yesterday.
The DfT said it was aware of the incident; the Rail Accident Investigation Branch said the incident happened on the 0554 service and was reported by operator Govia Thameslink Railway (GTR). The driver-only operated (DOO) train left a station with its doors open.
A spokesman for Southern said this could have happened even if there had been a guard on board.
Yesterday morning there was an operating incident at Reedham station involving the 0554 service from Tattenham Corner to London Bridge.
There was nothing wrong with the train and early indications are this was driver error in releasing the brakes before the doors had shut.
This allowed the train to roll downhill unpowered one coach length at low speed before the driver realised his error.
This was an unusually rare set of circumstances on a train that has run without a conductor for many years and could have happened even if there had been a guard on board.
GTR is involved in a long-running dispute with the Rail, Maritime and Transport (RMT) union over the future role of guards. Industrial action has been causing significant ongoing disruption for commuters.
At a meeting of the Transport Select Committee discussing rail franchising yesterday, rail minister Paul Maynard said he remained extremely frustrated over the ongoing industrial action.
"I continue to urge the RMT to put the needs of passengers first, to call off their strikes," he said, adding there were strikes going forward he couldn't "discern the underlying reason for". The union has repeatedly stressed it maintains its stance over safety, though the regulator has signed off DOO as being safe.
Maynard said he didn't accept RMT's argument over safety and he had "complete confidence in driver-only operations".