Two DPU sets trail a loaded Union Pacific coal train down the 2-percent grade out of Tunnel 1 between Plain and Clay, Colorado, on a snowy December 22, 2006. The mid-train DPU made up of two EMD SD9043MACs sandwiching a GE AC4400CW are passing the detector at mile 22.6, while lone EMD SD9043MAC No. 8141 as rear DPU holds down the back of the train on then other side of Coal Creek Canyon.
