I noticed UP coupling distributed power to stack cars on the rear of the train and then coupling TOFC behind the locomotive. This is on UP (CNW) west line out of Chicago.
I understand the reasoning but only saw it in hilly/mountain terrain.
You can see it on the Rochelle web can since it appears to be a common occurence.
I suppose that pushing on those light TOFC cars could cause them to derail. Pushing directly on the heavy stack cars and dragging the TOFC cars gives you a little of the swing helper effect. Hilly territory would exaggerate the amt of effort needed to lift the train and therefore the risk. High amts of curvature would do the same.
That would be interesting to see.
I can think of two other plausible operational reasons for this:
If it’s a particularly long train (I’ve forgotten what the length limit is…must be time to retire!), the DP units wouldn’t be able to be put at the end and still assure signal continuity.
Or, if the train has a block to be set out (for example, a train going to CSX 59th Street might have a Global 2 block to set off), this would be an easy way to do this and could probably save the need for a more extensive brake test, whether or not the DP units stayed on.
It is becoming more popular for long distance Intermodal to use DPU locomotives within the train to reduce in-train forces. CP runs a Vancouver - Toronto Intermodal in a 1x1x1 configuration with both DPUs cut into the train. This is expected to be the new normal for all their transcontinental Intermodals.
As well, here in South Central Kansas,Eastbound on the ElDorado Sub, the longer Stacks and Merchandise trains run with double end of train DPUs; while an ‘in-train’ single DPU is an occasional sight, but not unheard of. Recently, there have been more trains of TOFCs running with out DPUs, but much shorter lengths of train.
I have seen it (in train DPUs) more around the junctions at Mulvane, when the Northbounds are coming off the Ark City Sub and going up the ElDorado line to the NEast out of Mulvane area.
The distance between the rear of the head end consist and the front of the DP consist can’t be more than 8500 feet. If the the DP is equipped with an EOT repeater, they can tack on another 6500 feet of train for a total length of 15000 feet.
The manifest out of Council Bluffs for Proviso is now run DP. At Beverly they pick up behind the DP, except for high value (John Deere tractors out of Waterloo, IA) loads. These go on the head end behind the lead engines according to placement instructions. The only time I’ve had it (so far) since they started this, we had to pick up twice. First behind the head end consist, then put the train together and pick up behind the DP.
I haven’t seen or had one yet, but for about the last week or so one of the westbound auto rack trains is shown has being run DP. A while back instructions were issued allowing for 10000 foot DP auto rack trains on certain subdivisions.
Jeff