An Amtrak engineer involved in a train derailment that killed eight passengers turned himself in to police Thursday on charges including causing a catastrophe and involuntary manslaughter, in a case brought only after a victim's family got a judge to order that charges be filed.

Brandon Bostian, 34, was put in handcuffs as he arrived at the Philadelphia police station with his attorney.

Just minutes after leaving Philadelphia on May 12, 2015, on a Washington-to-New York run, Bostian accelerated to 106 mph on a 50 mph curve, sending his train careening off the tracks, an investigation by the National Transportation Safety Board found. In addition to the eight dead, about 200 passengers and crew were injured.

The agency found that Bostian essentially forgot where he was when he sped up.

Bostian, who has been on unpaid administrative leave from Amtrak, did not respond to reporters' questions as he entered the police station.

He told NTSB investigators he could only remember speeding up for an 120 kph straightaway and then hitting the brakes a few minutes later as he felt his body lurch and the locomotive starting to tip over.

Just days before a two-year statute of limitations was to expire, Philadelphia prosecutors announced last week that there was insufficient evidence to prove that Bostian acted with intent or "conscious disregard" for the passengers' safety.

Victim lawyers said that should be an issue for a jury to decide, and a judge acting on a private criminal complaint from one victim's family ordered misdemeanour charges filed.

Civil suit settled by Amtrak

City prosecutors then referred the case to Pennsylvania's top prosecutor, the state attorney general, who added a felony count of causing a catastrophe on top of eight misdemeanour counts of involuntary manslaughter and other charges.

The citizen complaint against Bostian was brought by attorneys for the family of Rachel Jacobs, a 39-year-old chief executive of a Philadelphia-based technology startup who was killed returning home to her husband and two-year-old son in New York.

Thomas Kline, an attorney for the family, said Thursday the state's prosecution of Bostian "ratifies the fact that there are important circumstances where citizens who are aggrieved and who follow the legal process can achieve justice."

"The district attorney's office was 100 per cent wrong and the attorney general's office is on a track to being 100 per cent correct," he said.

Amtrak has taken responsibility for the crash and agreed to pay $265 million US to settle claims filed by victims and their families.

The NTSB found no evidence that Bostian was impaired or using a cellphone. The agency also called Amtrak's long failure to implement automatic speed control throughout the busy Northeast Corridor a contributing factor.

Bostian has a personal injury suit pending against Amtrak. He said he was left disoriented or unconscious when something struck his train before it derailed. He had heard through radio traffic that a nearby commuter train had been struck by a rock. However, the NTSB concluded that nothing struck his locomotive.

"The best we could come up with was that he was distracted from this radio conversation about the damaged train and forgot where he was," NTSB chairman Christopher Hart said at a May 2016 hearing.

The train's data recorder showed that at about 55 seconds and a mile-and-a-half before the derailment, Bostian applied full throttle and held it there for about 30 seconds. The train reached a speed of about 152 kph.

The NTSB said he then slightly lowered the throttle for two seconds before returning to full throttle and holding it there for another 20 seconds. Three seconds before the derailment, at a speed of 170 kph, Bostian applied the emergency brake, which reduced the speed to 164 kph.