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III. ANALYSIS
Operation of Train 720
An expert witness calculated that the deformation of metal in the two demolished cars absorbed about 40 million foot-pounds of energy. This same witness concluded that the speed of train 720 at impact must have been between 44 and 50 m.p.h. This estimate is corroborated by a comparison of the movements of trains 720 and 718 before impact.
Train 720 was running abreast of an inexact location on 718; it never passed ahead of the third car on 718. Train 718 was traveling at a constant speed, estimated to be 60 to 65 m.p.h. The engineer of 720 estimated his speed at the signal as about 40 m.p.h., and he stated that he then reduced his speed even further.
If these estimates are accurate, the 20-m.p.h. average speed differential between the trains from the signal to the point of impact would have permitted all of train 718 to pass 720. This would also hold true for a 10-m.p.h. differential, i.e., with 720 traveling at 50 m.p.h. However, the evidence clearly indicates that at least the last car of 718 had not passed 720 when the collision occurred. Thus, the average speed differential between the trains for the 2,175 feet south of the impact point was slightly less than 10 m.p.h., and train 720 was probably traveling at an average speed of between 50 and 55 m.p.h.
Train 416 must have been backing past Signal 3-3.10 at about the same time as 720 passed Signal 3-3.60. Although 416 was not visible to the engineer of 720 at that point, the sight-distance tests indicated that the engineer should have seen 416 a considerable distance before the braking limits of 720 were overrun. For example, if one assumes closing speeds of 11 m.p.h. for train 416 and 52 m.p.h. for train 720, 416 should have been visible when it was at least 369 feet from the point of impact, and when 720 was 1,760 feet from impact. The emergency braking distance for a train similar to 720, traveling at 52 m.p.h., is less than 1,200 feet.
Therefore, if the emergency brakes on train 720 had been applied at the time 416 first should have been discernible to the engineer of 720, the train should have stopped before the point of impact. Furthermore, if 720 had been running, as required, at 30 m.p.h., prepared to stop short of Signal 3-3.10, an emergency brake application at the time the engineer stated he first saw 416 would have stopped 720 in sufficient time.
