Been seeing coal drags go past the cameras at Cresson and the Curve with AC traction DPUs on the rear instead of usual pairs of SD40E helper sets. I wonder how many fewer helper crews they are going without now. Do the DPUs get cut off at Altoona or do they go all the way through with the train to its destination? Used to be coal trains would have 2 helper sets on the rear for braking, if they are getting by with just one pair as DPUs now, are there track restrictions (i.e. these can't be sent down "the slide")?