About 5:30 a.m., mountain standard time, on October 11, 1996, a series of collisions occurred on the Union Pacific Railroad near Cheyenne, Wyoming. The collisions occurred when a runaway cut of cars with an unmanned single locomotive on the trailing end, collided head-on with a UP westbound freight train. Five empty ballast cars from the runaway train derailed fouling the adjacent mainline. A UP eastbound freight train travelling on the adjacent track struck a set of wheels from the derailed cars causing the derailment of their four locomotives and four sets of cars.

NTSB Report

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