If one considers that a long train of 100 cars may be 6000’ long, and that each car
might account for six inches of slack, it becomes mathematically possible for a
locomotive and the front end of a train to move fifty feet before the rear end moves at
all. As a result, the dynamic portion of the buff and draft forces can become quite
large if the operation of the train, or more importantly to the designer, the geometry of
the alignment contribute significantly to the longitudinal forces