(AP) The revelation that a New York City commuter train derailed while barreling around a sharp curve at nearly three times the speed limit is fueling questions about whether automated crash-avoidance technology could have prevented the carnage.



Safety officials for decades have championed what's known as positive train control technology, which uses GPS, wireless radio and computers to monitor trains and stop them from colliding, derailing or going the wrong way. But the railroad industry has sought to postpone having to install the systems 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 lawmaker said the derailment underscored the need for it.



"This incident, if anything, heightens the importance of additional safety measures, like that one," said U.S. Sen. 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 82 mph as it entered a 30 mph turn Sunday morning and ran off the track, National Transportation Safety Board member Earl Weener said Monday. He cited information extracted from the train's two data recorders; investigators also began interviewing the train's crew.



The speed stunned officials - "I gulped," said U.S. Sen. Charles Schumer, D-N.Y.



"Certainly we want to make sure that that operator is disciplined in an appropriate way. There's such a gross deviation from the norm, that there may be other agencies that also want to take a look at his behavior in operating the train," Gov. Andrew Cuomo said Tuesday. "That amount of speed is certainly unjustifiable."



Union leader Anthony Bottalico said he was confident the investigation would reveal there was no criminal intent.



"At this point in time, we can't tell" whether the answer is faulty brakes or a human mistake, Weener said.



Investigators began talking to the train's engineer Monday but were unlikely to continue the interview until Wednesday, National Transportation Safety Board spokesman Keith Holloway said Tuesday. He said he had no information on the reason; Bottalico said it was because William Rockefeller hadn't slept in almost 24 hours and was "very distraught."



Bottalico said the engineer planned to have a lawyer accompany him to the interview. The attorney didn't immediately return a call Tuesday.



The New York Police Department is conducting its own investigation with assistance from the Bronx district attorney's office in the event the derailment becomes a criminal case.



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.



It takes about a quarter-mile to a half-mile to stop a train going 82 mph, according to Kevin Thompson, a Federal Railroad Administration spokesman.



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.



"Billy is a very sincere guy. This is a man who is totally distraught by the loss of life, and he's having a tough time dealing with that," said Bottalico, the general chairman of the Association of Commuter Rail Employees.



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 percent of train accidents. 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.



Grady Cothen, a former FRA safety official, said a PTC system would have prevented Sunday's crash if the brakes were working normally. And Steve Ditmeyer, a former FRA official who teaches at Michigan State University, said the technology would have monitored the brakes and would not have allowed the train 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 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 $428 million 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 1,200 miles of track.



"It's not a simple, off-the-shelf solution," Anders said Monday.



On Sunday, the train was about half full, with about 150 people aboard, when it ran off the rails while rounding a bend where the Harlem and Hudson rivers meet. The lead car landed inches from the water.



The dead were identified as Donna L. Smith, 54, of Newburgh; James G. Lovell, 58, of Cold Spring; James M. Ferrari, 59, of Montrose; and Kisook Ahn, 35, of Queens.



Some of the injured remained hospitalized Monday, including seven in intensive care at one hospital and two patients in critical condition at another.



The train was configured with its locomotive in the back instead of the front. Weener said that is common, and a train's brakes work the same way no matter where the locomotive is located. Ditmeyer said the locomotive's location has virtually no effect on train safety.



Still, some people feel the configuration provides less protection for passengers because if the train hits something, there's no locomotive in front to absorb the blow, said Bill Henderson, executive director of the Permanent Citizens Advisory Committee to the MTA, a riders' advocacy group.



The derailment came amid a troubled year for Metro-North, and marked the first time in the railroad's 31-year history that a passenger was killed in an accident.



In May, a train derailed in Bridgeport, Conn., 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 garbage derailed near the site of Sunday's wreck.



Repair work on the latest derailment damage continued on Metro-North's Hudson Line, which normally carries 26,000 weekday riders.



On Monday night, workers used a backhoe to push pieces of damaged track off to the side, and then broke them up for disposal. On Tuesday, dozens of workers in orange vests were hammering new tracks into ties. There was heavy equipment along the tracks; one worker pounded with a mallet.