. >> reporter: doctor bucheck a renoun transportation expert and emeritus professor at university of pennsylvania has seen this happen before. he says in most train crashes two, sometimes three things go wrong but the the speed of the train, he says, is solely in the control of the engineer. in this case, brandon bostian a three two-year old with less than five years experience. how can you explain that train traveling that fast, at that particular place. >> he did something that is terribly wrong. so there must be some explanation. either in him, or certainly within him, yes. >> reporter: what that explanation is right now. >> i cannot guess. >> reporter: amtrak trains are equipped with a dead man's switch a device engineers must engage every 152nd or the train will stop indicating bostian was not incapacitated before the crash. he would have known the speed limit around the curve where it happened according to the professor bucheck since engineers are trained to operate on specific routes but one safe guard he did not have was positive train control a computerized gps based system