over the track changes the physics and the dynamics of the forces that you have in that curve. it's like racing a motorcycle. as you approach that curve, c t forces on the track. whether that train was entering a curve and like peter said, they will have that the black box. >> what you are saying is the difference of an empty train going into that curve as opposed to a train with 78 persons and crew members and presumably lots of luggage is a different environment, right? >> right. it's every kind of transportation accident, it's amazing how much a few pounds and a few changes in the forces on the vehicle can make. given there was so much criticism of starting this run