This is a good example of Distributed Power Units (DPU) in action. This train has two head-end units, three mid-train DPU's and a single DPU on the rear end of the train. All DPU's are controlled from the head-end, and can even be operated independently, meaning that the engineer can have his lead units switching over to dynamic braking as his train reaches the top of a grade, even while the mid-train and rear-end DPU's are still pushing at full throttle. Running these trains over the mountains is not a job for the faint-hearted.