It's time to put the derailment of Amtrak Train 188 to rest, to take the lessons learned from the tragedy and use them to prevent more harm.

Two years ago, engineer Brandon Bostian pushed the train's speed to dangerous levels causing it to fly off the tracks, killing eight and injuring more than 150. With the statute of limitations expiring Friday, the Philadelphia District Attorney's Office announced Tuesday that it would not be filing charges.

That was the right course. Bostian wasn't high or drunk. He wasn't on his cell phone. There has been no finding that he deliberately doubled the speed at the Franklin Curve just north of 30th Street Station. The National Transportation Safety Board says the engineer was distracted by radio talk concerning someone who threw a rock at a SEPTA train on the same tracks.

Bostian said he doesn't remember much from the moments before the accident. He was suspended without pay after it occurred, but remains an Amtrak employee. In January, he sued the rail service, accusing it of failing to provide a safe work environment and noting he hurt his head and back, and suffered psychological damage.

The engineer's mistake was truly cataclysmic. The lives lost and suffering of their survivors is incalculable. But no case has been made to prosecute Bostian. Any charges probably wouldn't stick. There was no proof that Bostian deliberately ignored the risk of speeding up the train.

That makes this disaster different from the devastating 2013 building collapse at 22nd and Market streets, where an unsupported wall fell on a Salvation Army thrift store, killing six and injuring seven. Another victim died later. In that case, there was evidence that the stingy building owner hired a cut-rate demolition contractor with no experience. The contractor was convicted of criminal charges.

Those wanting to point the finger of guilt at Bostian should widen their field of vision. The engineer's moments of distraction were made worse by Congress, which kept extending the deadline for the nation's railroads to install a braking system that could have compensated for Bostian's error. The Positive Train Control system automatically slows trains when they reach dangerous speeds.

PTC is a not a new technology. It has been around for years and pushed hard by the NTSB since at least the early 1990s. Delaying its installation along busy rail corridors was unconscionable and likely the difference in preventing numerous avoidable accidents. In fact, the NTSB said the system likely would have saved every passenger aboard Amtrak 188. The PTC system is now in place on tracks along the entire Northeast Corridor except for a portion just north of New York City.

Amtrak rightly took responsibility for the Philadelphia derailment and has agreed to a $265 million settlement that must be divided. Meanwhile, Congress has required that PTC be in place on all heavily traveled tracks by 2018. There should be no more extensions of that deadline, no more needless tragedies, no more blame directed at one person when the negligence of others – from the railroad to Congress – was also responsible.