The National Transportation Safety Board has released its findings on the horrific Amtrak train wreck north of the Philadelphia 30th Street Station on May 12, 2015, and finds no smoking gun.
There is no clear explanation as to why the train, under engineer Brandon Bostian, sped up as it approached a curve. One is still somewhat left with the idea that some sudden event distracted him, and that could have been an object, possibly thrown or shot, hitting the locomotive. This could be prosecutable as a crime, like pointing a laser at an airplane. Or possibly the (previous) lack of automated positive train control simply leaves engineers open to rare but catastrophic human error.
There are some YouTube videos advancing “conspiracy theories”.
Atlantic weighs in with “The Mystery of Amtrak 188”.
I’ve ridden the route countless times, finding recently that the Acela is more reliable (doesn’t have to stop) and doesn’t cost much more if bought in advance.
Back in the 1970s, it used to be common for some trains to make an additional stop at “North Philadelphia”.
Update: May 17, 2015
ABC News reports distraction of the train's engineer by radio reports of rocks hitting another train, link.