Yonkers - The revelation that a New York City commuter train derailed while barrelling into a sharp curve at nearly three times the speed limit is fuelling questions about whether automated crash-avoidance technology could have prevented the carnage.
Safety officials have championed what's known as positive train control technology for decades, but the railroad industry has sought to postpone having to install it because of the high cost and technological issues.
Investigators haven't yet determined whether the weekend wreck, which killed four people and injured more than 60 others, was the result of human error or mechanical trouble.
But some safety experts said the tragedy might not have happened if Metro-North Railroad had the technology, and a senator said the derailment underscored the need for it.
"This incident, if anything, heightens the importance of additional safety measures, like that one," said US Senator Richard Blumenthal, a Democrat from Connecticut, which also is served by Metro-North. "I'd be very loath to be more flexible or grant more time."
The train was going 132km/h as it entered a 48km/h turn on Sunday morning and ran off the track, National Transportation Safety Board member Earl Weener said on Monday.
He cited information extracted from the train's two data recorders; investigators also began interviewing the train's crew.
New York Governor Andrew Cuomo said the NTSB findings make it clear "extreme speed was a central cause" of the derailment and vowed to "make sure any responsible parties are held accountable" after investigators determine why the train was going so fast.
Weener sketched a scenario suggesting that the throttle was let up and the brakes were fully applied way too late to stave off the crash.
He 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 not aware of any problems with the brakes during the nine stops the train made before the derailment, Weener said.
Weener would not disclose what investigators know about the engineer's version of events, and he said the results of drug and alcohol tests were not yet available.
Investigators are also examining the engineer's cellphone; engineers are allowed to carry cellphones but prohibited from using them during a train's run.
The engineer, William Rockefeller, is cooperating with investigators, said Anthony Bottalico, executive director of the rail employees union. Rockefeller, 46, has been an engineer for about 11 years and a Metro-North employee for about 20, he said.
Positive train control, or PTC, is designed to forestall the human errors that cause about 40% of train accidents, and uses GPS, wireless radio and computers to monitor trains and stop them from colliding, derailing or going the wrong way.
The transportation safety board has urged railroads to install PTC in some form since 1970, and after a 2005 head-on collision killed 25 people near Los Angeles, Congress in 2008 ordered rail lines to adopt the technology by December 2015.
Metro-North has taken steps toward acquiring it but, like many rail lines, has advocated for a few more years to implement a costly system that railroads say presents technological and other hurdles.
The Metropolitan Transportation Authority, which runs Metro-North, began planning for a PTC system as soon as the law was put into effect, spokeswoman Marjorie Anders said.
After some early-stage work such as buying radio frequencies, the MTA awarded $428m in contracts in September to develop the system for Metro-North and its sister Long Island Rail Road.
But the MTA has advocated for an extension to 2018, saying it's difficult to install such a system across more than 1 000 rail cars and 1 900km of track.