Negotiating the curves entering Clay, Colorado, on the Moffat Tunnel Subdivision is an eastbound Burlington Northern Santa Fe coal train on the afternoon of July 5, 2003. The head end is already at Clay, and is helped by a mid train DPU, which is about 3/4 of the way back in the train, and a manned helper set of two former BN SD40-2s holding down the rear of the train, that has just crossed Blue Mountain Drive grade crossing.