Passenger train goes through red lights outside London
Accident investigators are looking into how passenger train travelled nearly two miles after going through two red lights just outside London Paddington.
The Chiltern Railways service from London to West Ruislip in west London ended up on a single-track section which was occupied by a freight train.
An emergency radio message was eventually got to the passenger train which stopped and no-one was hurt in the incident on March 20 2014.
The Rail Accident Investigation Branch (RAIB), which is probing the incident, said the train protection and warning system (TPWS) which prevents collisions had "self-isolated" - become inoperable - when the driver prepared the train for departure from Paddington station in London.
"Although the isolation of the equipment was indicated by a flashing light in the cab, the train was driven with the TPWS isolated," the RAIB said.
A freight train had passed the junction at Greenford in west London shortly before the passenger train was due. Because this train was still occupying the line between Greenford and South Ruislip, the signaller at Greenford kept the signal at the junction at danger.
The RAIB said the passenger train, travelling at about 20mph, passed this signal and the next one, 142 yards (130 metres) further on, which was also at danger.
It passed over the junction and onto the single-track section towards South Ruislip, which was still occupied by the freight train.
The signaller at Greenford was unable to send an emergency radio message to the driver, but contacted the signaller at Marylebone signalling centre who was able to do so. The train was stopped after it had travelled about 1.75 miles past Greenford.
The RAIB said its investigation "will seek to understand why the TPWS self-isolated, why the driver did not identify that the TPWS equipment was isolated and rectify the problem, and also why he did not respond to the signals at danger at Greenford."
It added: "It will consider Chiltern Railways' arrangements for training, briefing and assessing the competence of drivers.
"The investigation will also consider the operation of the signals at Greenford and the reasons why the signaller was not able to transmit a radio message to the driver after the train had passed the signals at danger."
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