At one time the NS put a bulletin out to have the smaller DC units in the lead. When I first started to run I was told the N&W had the same instructions ,and according to my late Dad the C&O done this also.
Shortly after the NS merged with Conrail and we started experiencing the AC units there was a bulletin out saying "managers" and crews should try to have AC units ahead of DC .
With todays tonnage and unit rating instructions on our orders , the orders specifically tell us according to our tonnage and our train route , what units in the consist we are to have online from point A to point B .
The technology is there now for the consist to start dropping units "out" that you have online while en-route , but I'm not sure if it's being utilized .
AC's has been a learning curve for the railroads and crews alike.
The AC's have had software changes that has helped the "chattering" of the wheels going into dynamic braking and the "surge" that Engineer's have experienced like mentioned when starting a train out on grade.
Now with more trains using DP power in the middle or on the rear some of this AC problems have been eliminated making the trains smoother starting out and operating down the road.
There's still bugs and learning curves even with the DP trains , especially when using PTC .
But the units both AC and DC will limit themselves on amperage when they get hot due to prolonged continuous amperage or simply will quit loading . The only way you can see while on the move the information on trailing units such as amperage , is if the units are say all newer GE's ,then I have seen the lead units computer show you another GE units information . You just cannot "manage' it .Again I believe the technology is there to do so but at this point were not using it on the NS.
