The Amtrak engineer at the controls of a speeding train that derailed in Philadelphia last year, killing eight people, was distracted in the moments before the accident, U.S. investigators are preparing to conclude at a meeting Tuesday.

The National Transportation Safety Board’s staff is proposing that a rock-throwing incident involving a separate commuter train, which the engineer knew about because it was discussed in radio broadcasts, most likely led him to lose awareness of speed limits, two people briefed on the discussions said. They asked not to be identified because they weren’t authorized to speak about the matter before the meeting.

In addition to the dead, more than 200 were injured when the train carrying 238 passengers derailed in a shower of sparks on May 12, 2015, as it sped into a curve at speeds as high as 106 miles (171 kilometers) an hour, more than twice the limit.

Another issue that will be discussed by the NTSB is technology known as Positive Train Control that would have prevented the accident by automatically limiting the train’s speed, the people said. Since the accident, Amtrak completed installing PTC on rails it controls in the corridor between Washington and Boston.

Board Debating

Board members at the NTSB, who have final say on what the report will conclude, were still debating some of the issues, the two people said. They could alter the staff’s recommended findings and change the emphasis somewhat, they said.

Evidence at the scene and a black-box recorder on the train have given investigators a clear picture of how the train was operated and allowed them to rule out such things as mechanical failures. But there is scant evidence of what was going on in engineer Brandon Bostian’s head.

Bostian, 31 at the time of the accident, was in good health, hadn’t been distracted by a mobile phone and tested negative for drugs, according to investigators. After being hit on the head in the collision, he doesn’t remember what happened in the moments before impact, he told the NTSB.

At Controls

“I remember turning on the bell, and the next thing that I remember is when I came to my senses I was standing up in the locomotive cab after the accident,” he told investigators a year ago.

Bostian was at the controls when the train sped up, suggesting that he commanded the increase.
The stretch of tracks just beyond the curve had a speed limit of 110 miles an hour.

Even without a clear idea of what led Bostian to speed up, the accident will allow the NTSB to push for automated technology that could prevent such mishaps in the future and to emphasize the need for transportation workers to avoid distractions.