Emergency personnel work at the scene of a derailment in Philadelphia of an Amtrak train headed to New York in 2015. The National Transportation Safety Board meets Tuesday, to detail the cause of last year's fatal derailment. (Patrick Semansky/AP)

The horrific Amtrak wreck that killed eight people and injured 159 in Philadelphia last year could have been prevented if hardware installed on the train had been switched on, according to investigators.

The engineer also might have been distracted by radio traffic about rock throwing involving a SEPTA commuter train, although he told investigators last year that he was not overly worried by the incident.

Those factors are among those expected to be discussed when the National Transportation Safety Board meets Tuesday to announce the results of its year-long investigation into the Amtrak wreck.

Seven months after the passenger rail line suffered its worst wreck in 22 years, Amtrak flipped the switch to activate the system that could have slowed the speeding train, complying with a then federal deadline that mandated installation of Positive Train Control (PTC) by the year’s end.

If PTC had been activated before engineer Brandon Bostian allowed the train to hurtle into a sharp bend in the tracks at more than twice the posted speed limit, the system automatically would have slowed its speed.

Emergency personnel help a passenger in Philadelphia after the derailment of an Amtrak train on May 12, 2015. (Joseph Kaczmarek/AP)

NTSB investigators have determined that Bostian was sober, drug free and not on his cell phone when he let the train speed into the fatal turn. But he told investigators that a radio report of rocks being thrown at a commuter train concerned him.

“I wasn’t, you know, super concerned, I don’t think,” Bostian told investigators a year ago in the first of two long interviews with them.

The report of rocks or, perhaps, bullets being fired a commuter rail train operating on adjacent tracks was the first indication the Bostian might have been distracted. He heard radio conversation between the operator of the SEPTA train and his dispatcher, and then contacted the operator himself.

“There’s been so many times that I’ve had reports of rocks that I haven’t seen anything, that I felt it was unlikely that it would impact me,” Bostian, 32, told investigators on May 15, 2015. “And I was really concerned for the SEPTA engineers.

Asked if he was fearful himself, he said “Slightly.”

“But I figured there’s a good chance that they left,” Bostian said. “Whoever was throwing the rocks had probably left.”

With all of the train’s systems apparently functioning normally, Bostian’s actions became a key focus of the investigation. He told investigators he had a “very foggy memory” of what went on as he passed through North Philadelphia piloting a train that originated in Washington’s Union Station and was bound for New York City.

“The memory from there is very vague,” Bostian told investigators in November, six months after the crash. “The only word, and I hesitate to use the word ‘dreamlike’ because it sounds like I was asleep, and I don’t believe that I was asleep at all.”

At that moment — seconds before the engine and several of the seven cars it was pulling left the tracks — the train was going 106 miles per hour, more than twice the 50 mph limit for the sharp curve to the left, the train’s event recorder indicated.

[Engineer in Philadelphia Amtrak derailment recalls ‘foggy’ memory]

“The memory doesn’t include much visual memory. I don’t remember hearing much. It was more of a feeling,” he said. “I remember feeling my body lurch to the right, towards the right side of the engine. I remember feeling as though I was going too fast around a curve. In response to that feeling, I put the train brake on.”

The wreck of Amtrak train 188 left rail cars strewn like toppled bowling pins beside the Frankford Junction tracks. One ripped open in a contortion of aluminum that left little looking like a rail car. Others, whipped off the tracks at 103 miles per hour, landed on their sides. Passengers hit the ceiling, flew out of broken windows, landed atop one another, were struck by flying luggage or were crushed in the twisted wreckage.

In addition to the eight dead, 46 people were seriously injured and 113 others suffered lesser injuries.

Outside safety experts and engineers have been mystified, caught between the real questions they say Bostian’s actions raise and their own reluctance to condemn him in the absence of clear information.

Bill Keppen, a rail safety expert who was himself an engineer on freight line Burlington Northern for 13 years, said the radio chatter in Philadelphia about a commuter train being struck by an object would not have been particularly unusual or all-consuming for an engineer.

“It would not be uncommon for trains or engineers to communicate about troubles along the railway. I don’t think that would really affect the guy’s concentration,” Keppen said. “I can’t see inside that guy’s brain. That’s his brain. I would be alert, but I wouldn’t be afraid.”

Given the strength of the glass in cabs, it’s unlikely an object could do more than crack the glass, and would likely not lead to an injury, Keppen said. Bostian told investigators he was thinking about an associate who was indeed hurt by getting shattered glass in his eye in such an incident.

“I hesitate to criticize the guy. He’s going to live with that for the rest of his life,” Keppen said.

The blurry nature of Bostian’s recollections have made drawing lessons, a primary goal of such NTSB exercises, difficult. But one thing is clear, he said.

“It points to the importance of having technology like positive train control fully operational,” Keppen said.

PTC has been called “arguably the single-most important rail safety development in more than a century” by federal regulators.

Federal Railroad Administration head Sarah Feinberg threatened to fine passenger and freight railroads last year when a year-end deadline for its installation approached. But the railroads contended they had too little time to install the complicated system, and Congress listened to their plea and extended the deadline until 2018.

[Feds tell railroads they must meet deadlines for live-saving technology]

Congress, whose members have received more than $24 million in campaign contributions from the powerful railroad industry since 2008, also said railroads could ask for up to two additional years after the 2018 deadline to complete the job.

Feinberg made clear that she expects regular progress reports from railroads, some of which have systems nearly complete, while many others are well behind.

Fearful that some railroads may think the wiggle room granted by Congress gives then until 2020 to finish installation, Feinberg has warned that unless railroads meet FRA benchmarks, no extensions will be granted beyond 2018.

Though Amtrak owns most of the rail on which its trains run in the Northeast Corridor, the balance of it’s operations are on track owned by freight rail roads. To complete the PTC system, those freight railroads must install a system of way points with which equipment on board the train maintains contact.

[Deadline for train safety technology undercut by industry lobbying]

Aware of FRA criticism, the Association of American Railroads, a trade group for the freight lines, said Monday that it’s members have invested $6.5 billion dollars on PTC. They said the cost will climb to $10.6 billion to cover the 60,000 route miles of freight rail track.

“Freight railroads continue to aggressively move forward with testing and installation of PTC on their individual networks,” said AAR spokesman Ed Greenberg. “The freight rail industry remains on schedule at having PTC fully implemented across the country as quickly as possible and in accordance with the extension passed by Congress.”