resulted from going into a corner too fast like this one in philadelphia in 2015 or a section of track blocked misaligned. now they're asking why this train went off the rails when the track was straight. >> it's got something with the train cars themselves and how they connected with the track or some fault or flaw in the track. >> reporter: on a per-mile basis, rail travel is far safer than traveling by car, and recent years have seen safety improvements like positive control systems that automatically keep trains at safe speeds, but rails are a constant challenge. it will be one area that investigators will examine as crews work to clear the area of this well traveled rail corridor. >> our thanks to jake ward. still ahead, what's being