Eastern Railroad Discussion > DPU location

What are the considerations that go into placing a DPU engine in the middle of the train vs putting it on the end of the train?
I have never seen it, but do they ever do both?

Midtrain DPU and end of train DPU may be seen in ore trains, coal trains, etc among others.

Once in a while you may see midtrain, end of train, and manned helpers on the Horseshoe Curve camera.

Posted from Android

Double PRB coal loads have been frequently observed with mid- and end-of-train DPUs. 

You will see all sorts of combinations. 1, 2 or 3 head end 1 or 2 midtrain and 1 on the hind end but anything is possible. Why? I don't know but 2X1X0 seems most common. In 1995 when I first moved here along the ex-Reading Mainline Conrail moved import iron ore to I believe Ohio, but the Bethlehem, PA furnaces may have still been operating, using then new GE distributed power 3X2X0. The returning empties were 5X0X0. This was some of the earliest GE DPU used.
Gonut

FatSquirrel Wrote:
-------------------------------------------------------
> What are the considerations that go into placing a
> DPU engine in the middle of the train vs putting
> it on the end of the train?
> I have never seen it, but do they ever do both?

As stated, routine for BNSF and UP on PRB coal trains as seen here: https://www.trainorders.com/discussion/read.php?1,6116958
On UP, I believe the first DPU can be no further than 8,500' back from the controlling locomotive.

mike woodruff
anacortes wa

I do know on CSX coal trains that leave the Oaktown, IN mine if the train is going from Nashville to Chattanooga then the DPU is mid train. I assume this is so power can be put on the rear at Nashville to assist in the mountains. If the train goes Nashville to Birmingham then the DPU can be on the rear.
I think on freights they have to watch the tonnage between the head end power and the DPU? I have heard on the radio before talk of having to move the DPU due to a set out or pick up of cars due to an imbalance of tonnage. Hope the more informed can school me on this.

Does CSX have differing lengths for the distance from head end to first DPU?

I've heard 7500 feet and 8000 feet. Does this depend on terrain, mountains, tunnels? I had heard that CSX installed ground repeater units for troublesome locations

Posted from Android

Back in the years of Southern's "radio trains", the mid-train unit was often about 2/3 of the way back in the train. I assume this was to achieve the fastest possible dump of trainline air throughout the train during an emergency brake application. 

In most cases it's up to the dispatcher, since there are many factors in the decision; length and weight of train, placement of loads vs empties, but most of all the grades and curves ncounterred on the trip.

Several factors go into it. The DP departing initial terminal (were I work) has to be between a certain percentage of the train's length. It can't be more than 8500' from the head end. Then can't have more than 75% of the rated tonnage behind the DP engine.

Posted from Android

OHRY Wrote:
-------------------------------------------------------
> Several factors go into it. The DP departing
> initial terminal (were I work) has to be between a
> certain percentage of the train's length. It can't
> be more than 8500' from the head end. Then can't
> have more than 75% of the rated tonnage behind the
> DP engine.
>
> Posted from Android

Is that rule typical across the railroad or is it a regional or divisional rule?

swaool Wrote:
-------------------------------------------------------
> FatSquirrel Wrote:
> --------------------------------------------------
> -----
> > What are the considerations that go into placing
> a
> > DPU engine in the middle of the train vs
> putting
> > it on the end of the train?
> > I have never seen it, but do they ever do both?
>
> As stated, routine for BNSF and UP on PRB coal
> trains as seen here:
> https://www.trainorders.com/discussion/read.php?1,
> 6116958
> On UP, I believe the first DPU can be no further
> than 8,500' back from the controlling locomotive.
>
> mike woodruff
> anacortes wa

This is the general rule of thumb, but there are exceptions.

PRR1361 Wrote:
-------------------------------------------------------
> In most cases it's up to the dispatcher, since
> there are many factors in the decision; length and
> weight of train, placement of loads vs empties,
> but most of all the grades and curves ncounterred
> on the trip.

Really? I can't imagine a railroad allowing the dispatcher to determine train make up. Things must be different in the east.

portlander Wrote:
-------------------------------------------------------
> PRR1361 Wrote:
> --------------------------------------------------
> -----
> > In most cases it's up to the dispatcher, since
> > there are many factors in the decision; length
> and
> > weight of train, placement of loads vs empties,
> > but most of all the grades and curves
> ncounterred
> > on the trip.
>
> Really? I can't imagine a railroad allowing the
> dispatcher to determine train make up. Things must
> be different in the east.

Portlander— you are correct, I’m not aware of any railroad on the east coast that lets a dispatcher dictate whether train can be or should be DP. Now that doesn’t mean the “the network” wouldn’t ask for train to be a restricted to certain length if there were meeting or passing length issues.

In the winter months most most dispatchers prefer a train to be DP if capable for the simple fact there are usually less air troubles.

Posted from iPhone

It happens all of the time, just not as often in the east. If you haven't seen a port stack over Cajon or a double grain in the PNW on BNSF or UP, look it up
Gone66 has a number of videos on TO showing multiple DPU locations, check them out. 

If you want to know how UP determines where a DPU is placed, I posted the UP Special System Instuctions. Go to Section 5-C, but read up first what Equivalent Powered axles and Equivalent Dynamic Brake axles are. I know a similar formula was used at my former employer.
UP SSI
FatSquirrel Wrote:
-------------------------------------------------------
> What are the considerations that go into placing a
> DPU engine in the middle of the train vs putting
> it on the end of the train?
> I have never seen it, but do they ever do both?



Edited 1 time(s). Last edit at 04/06/26 20:30 by Mojacket.

portlander Wrote:
-------------------------------------
> Really? I can't imagine a railroad allowing the
> dispatcher to determine train make up. Things must
> be different in the east.

It's not different. He doesn't know what he's talking about.

Posted from Android

Lackawanna484 Wrote:
-------------------------------------------------------
> OHRY Wrote:
> --------------------------------------------------
> -----
> > Several factors go into it. The DP departing
> > initial terminal (were I work) has to be between
> a
> > certain percentage of the train's length. It
> can't
> > be more than 8500' from the head end. Then
> can't
> > have more than 75% of the rated tonnage behind
> the
> > DP engine.
> >
> > Posted from Android
>
> Is that rule typical across the railroad or is it
> a regional or divisional rule?


That is a system rule.

bioyans Wrote:
-------------------------------------------------------
> portlander Wrote:
> -------------------------------------
> > Really? I can't imagine a railroad allowing the
> > dispatcher to determine train make up. Things
> must
> > be different in the east.
>
> It's not different. He doesn't know what he's
> talking about.
>
> Posted from Android

That would make more sense. . .

OHRY Wrote:
-------------------------------------------------------
> Lackawanna484 Wrote:
> --------------------------------------------------
> -----
> > OHRY Wrote:
> >
> --------------------------------------------------
>
> > -----
> > > Several factors go into it. The DP departing
> > > initial terminal (were I work) has to be
> between
> > a
> > > certain percentage of the train's length. It
> > can't
> > > be more than 8500' from the head end. Then
> > can't
> > > have more than 75% of the rated tonnage
> behind
> > the
> > > DP engine.
> > >
> > > Posted from Android
> >
> > Is that rule typical across the railroad or is
> it
> > a regional or divisional rule?
>
>
> That is a system rule.

Thanks for that info.