Amtrak Train 188 accelerated as it approached the curve at Frankford junction, National Transportation Safety Board investigator Robert Sumwalt said at a press conference Thursday.
A track image recorder revealed the train steadily gained speed in the minute before it derailed Tuesday night, killing eight people and injuring more than 200 others.
The engineer, who has agreed to speak with NTSB investigators, applied the emergency brake just before entering the curve, Sumwalt said. But it was too late to prevent the train from derailing.
“I’ll describe it as mere seconds into the turn — we can see the train tilting approximately 10 degrees to the right,” Sumwalt said. “And then the recording went blank.”
The forward-facing recording showed the train was traveling at 70 mph 65 seconds before the recording went blank, Sumwalt said. The train continued to gain speed, hitting 100 mph 16 seconds before the recording ended.
The recording is one of the several methods of investigation used by the NTSB on Wednesday.
Sumwalt said investigators began interviewing injured passengers, seeking to determine any injury patterns based on their seating locations. He said engineer Brandon Bostian agreed to be interviewed in the next few days.
Bostian did not provide Philadelphia police with a statement after the accident. He hired a lawyer, who told ABC news that Bostian did not remember deploying the emergency brakes and had “no explanation whatsoever” for the crash.
Sumwalt said the recording does not indicate whether the train increased speed manually.
“When we interview the engineer we would like to find out those types of things,” Sumwalt said. “It just shows the speed alone. It doesn’t tell how the speed got there.”
The train, which was traveling from Washington to New York, was on schedule when it departed 30th Street Station in Philadelphia, Sumwalt said.
Sumwalt said positive train control technology, which has not been installed on that section of the tracks in Port Richmond, would have prevented the accident.
“One of the four things it is designed to do is to prevent an overspeed derailing,” Sumwalt said. “Here, we are looking at an overspeed situation that did derail.”
Investigators also interviewed the Amtrak manager who was responsible for training and qualifications, tested train control signals, and completed on-site, 3-D laser scanning of the first two train cars.
Investigators did not find any anomalies when they examined the train’s pre-departure inspection records from Union Station in Washington, Sumwalt said. Investigators also will review track inspection records.
All transportation workers are required by federal law to undergo drug and alcohol testing after accidents. Sumwalt said the toxicology test results of Amtrak crew members are not yet known.