Investigators and first responders work near the wreckage of Amtrak Northeast Regional Train 188, from Washington to New York, that derailed yesterday May 13, 2015 (AFP Photo).
Investigators on Friday sought to explain why an Amtrak train that crashed in Philadelphia had accelerated in the minute before it derailed, putting a sharper edge on questions over the engineer's responsibility for the fatal accident.
A much-anticipated interview with the engineer, Brandon Bostian, could provide a major piece of the puzzle, federal investigators say.
The National Transportation Safety Board (NTSB) has said the train sped up from about 70 miles per hour (113 km per hour) to 100-plus mph in the 65 seconds before the crash, based on a video taken by the locomotive's front-facing camera. The NTSB is investigating what caused the acceleration.
Earlier, investigators disclosed that Bostian, 32, had slammed on the emergency braking system seconds before the wreck, as the train entered a curve. That slowed the train to 102 mph, or twice the speed limit on that stretch, before it derailed, killing eight passengers and injuring more than 200 others.
Experts said the train's speed in the moments before the crash raised several questions: Could a technical glitch have caused the locomotive to speed up so rapidly? Would it take a deliberate action by the engineer? Or could human error, a medical issue, or some other factor like clumsiness explain the sudden burst of speed?
The agency hopes to interview the engineer in the "next few days," said Robert Sumwalt, an NTSB member, after Bostian recuperates sufficiently from a concussion suffered in the
Tuesday evening crash.
That meeting was underway on Friday afternoon, NBC News said, citing unnamed sources. The NTSB, which will hold its next media briefing at 8:30 pm(local time) on Friday, declined comment on the report.
Steve Sullivan, a conductor turned consultant at RL Banks and Associates, said it was unlikely that a mechanical issue with the locomotive caused the acceleration, though the NTSB has not ruled out that possibility. Sullivan said he never heard of a train accelerating without someone moving the throttle.
The throttle of the locomotive that Bostian was operating has eight settings, with each click forward accelerating the train, said Charles Culver, a certified conductor and engineer based in
Texas who is not connected to the investigation.
Culver said it does not take much force to move the throttle forward and it was possible the engineer could have fallen and moved the throttle. Passenger trains, unlike freight trains, can increase speed rapidly, he said.
"In order to increase the speed as much as it was increased in this case, you would have had to really, really move the throttle," Culver said. "Frankly, I am puzzled about the whole thing."
All engineers are required to know speed restrictions on their routes, but Culver said it was possible the engineer lost awareness of the train's location due to some medical condition, such as a stroke.
Sullivan offered another possible scenario, though it was entirely speculative: "Something distracted him. He lost focus, and he thought he already went through the turn and that's why he was accelerating," the consultant said.
The engineer's attorney, Robert Goggin, has said Bostian was unable to recall much about the derailment, but his memory could improve as the effects of the concussion subside.
Goggin has also said Bostian had turned off his cell phone, as Amtrak requires of all engineers behind the controls.
In a briefing to reporters on Thursday, the NTSB's Sumwalt said federal law requires transportation personnel involved in an accident to be tested for drugs or alcohol but that it takes time for the results to come back.
Contrary to speculation that the driver might have been running late, Sumwalt also said that just 10 minutes before the crash, the train had departed its previous stop on time.
"Excellent Acceleration Capabilities"Federal investigators are still considering other possible factors in the sudden acceleration, including mechanical issues with the locomotive.
In service for just over a year, the locomotive was an Amtrak Cities Sprinter 64, or ACS-64, powered by overhead electric lines, the NTSB said.
That type of locomotive has "excellent acceleration capabilities" to sustain speeds of 125 mph while pulling up to 18 coaches, according to an Amtrak document seen by Reuters.
The document says an on-board computer system can notify the engineer of any maintenance issues and can take self-corrective action to maintain operation of the locomotive and ensure safety.
Sumwalt said there were no known problems involving unintended acceleration with this type of locomotive, but added that the agency would look closer into that possibility