A safety expert has said a fatal rail crash in New York could have been avoided if crash-avoidance technology had been installed.
The commuter train that derailed on Sunday killing four passengers was moving at 82mph as it entered a 30mph curve, but US government investigator Earl Weener said it was unclear whether the carnage was the result of human error or mechanical trouble.
Weener, of the National Transportation Safety Board, said the throttle went to idle six seconds before the derailed train came to a complete stop – "very late in the game" for a train going that fast – and the brakes were fully engaged five seconds before the train stopped.
Investigators are examining the mobile phone of train engineer William Rockefeller to determine whether he was distracted and are awaiting results of drug and alcohol tests.
But Steve Ditmeyer, a former Federal Railroad Administration official who now teaches at Michigan State University, said the tragedy might have been prevented if rail operator Metro-North Railroad had installed automatic-slowdown technology designed to prevent catastrophes caused by human error that safety authorities have been urging for decades.
Metro-North's parent agency and other railways have pressed the US government to extend Congress' 2015 deadline to install the technology for a few years because of the cost and complexity of the Positive Train Control (PTC) system, which uses GPS, wireless radio and computers to monitor trains and stop them from colliding, derailing or going the wrong way.
Ditmeyer said the technology would have monitored the brakes and would not have allowed the train in Sunday's tragedy to exceed the speed limit.
"A properly installed PTC system would have prevented this train from crashing," he said. "If the engineer would not have taken control of slowing the train down, the PTC system would have."
The train was about half full, with about 150 people aboard, when it went off the rails at around 7.20am while rounding a bend where the Harlem and Hudson rivers meet. The lead car landed inches from the water. In addition to the four people killed, more than 60 were injured.
Rockefeller, 46, was injured and "is totally traumatised by everything that has happened," said Anthony Bottalico, executive director of the rail workers union. He said Mr Rockefeller was co-operating fully with investigators.
"He's a sincere human being with an impeccable record that I know of. He's diligent and competent," Bottalico said. Rockefeller has been an engineer for about 11 years and a Metro-North employee for about 20, he said.
Asked whether the tragedy was the result of human error or faulty brakes, Weener said: "The answer is, at this point in time, we can't tell." But he said investigators were not aware of any problems with the brakes during the nine stops the train made before the derailment.
The derailment came amid a troubled year for Metro-North and marked the first time in the railway's 31-year history that a passenger was killed in an accident.
In May, a train derailed in Bridgeport, Connecticut, and was struck by a train coming in the opposite direction, injuring 73 passengers, two engineers and a conductor. In July, a freight train full of rubbish derailed near the site of Sunday's crash.