My drive to and from work follows one of the main BNSF Railway routes through Oklahoma, and during my commute I have had plenty of chances to observe mile-long freight trains, as well as the Amtrak Heartland Flyer. I grew up with a fascination with all things rail, and I guess it never wore off, since I have noticed something most of my friends have not: there seem to be a whole lot more locomotives pulling/pushing these trains lately. Growing up, it seemed like there was usually one pair of locos pulling the train as multiple unit operation…if it was a longer train, there might be a third, and one very rare occasions, a single loco pushing in the rear. I’ve noticed now that it’s more likely for there to be two pairs pulling, and it is now rare NOT to see one bringing up the rear.
Quick Google searches haven’t revealed any insight into the additional locomotives, nor has BNSF’s website, although I imagine this topic isn’t really PR worthy. My personal conclusion is that with the increases in the cost of diesel fuel, using more tractive power results in more fuel efficiency, but I’m curious if there is more at work here than just fuel economy.
I’m also curious if this trend of using more locomotives is happening with other railways…Oklahoma is pretty much BNSF territory, it’s rare to see any of the other lines around, so I haven’t had a chance to observe how they are using their locos.
The big thing is that automation has allowed for more widespread use of distributed power. When you have all the locomotives at one end of the train, the couplers on the cars near the front of the train have to transmit all the force necessary to pull the ones in the back (drawbar pull). In the past, this was one of the big limiters of train length. With locomotives at either end and/or in the middle, the couplers only “feel” a portion of the train weight.
Distributed power has been common in mountainous areas for a long time, but its use to make longer trains in the flatlands is a relatively new development. Just from casual train-nerdery, it seems like BNSF uses DP more frequently, but I think I have seen Union Pacific using it, especially for coal trains.
Union Pacific has been using DP too, generally with one unit pushing at the end of the train. I first noticed it about a year or two ago on the end of intermodal trains, but now I see them on just about everything, including manifests.
The formula for assigning a number of locomotives is pretty straightforward and depends on the weight of the train, its length, grades, etc. Usually, you’ll see more locomotives on loaded trains than empty (discounting things like power moves and whatnot.) Each subdivision has a timetable that outlines how many powered axles are allowed (most modern diesel electric locomotives have 6 powered axles, although there is a trend now to de-power the center axle on each truck.)
The railroads have been recovering very nicely from the Great Recession, and traffic has tended to be up over the past several years, so I’d expect the trend to continue.
UP runs the old KATY line over here in eastern OK. It basically parallels US69 from Texas up to Kansas. It’s just a single track with sidings for passing but lots of traffic. It’s rare to see a construct now without DP. All the coal trains use it. The two/three daily coa trains are a semi-permanent construct to match the loading and unloading loops. The tank car and general mashup trains are mostly DP as well. Lots of grain traffic with an occasional overlength construct which must have right of way. I’ve seen those with lead units, a center unit, and a pusher. As said, it’s easier on the equipment and probably manages the braking and acceleration better.
US coal exports has gone up more than 50% (with many coal plants in the US not getting permits and the demand for coal in Asia skyrocketing) - see here
This is a complete guess but I am thinking the bigger trains (and hence the dual locomotives) are to support the size of the ships transporting the coals. They may not want to have a huge storage facility at the port and may have a system where a train is directly unloaded to a ship - and having a train fit the size of the ship cuts costs down.
Arrrggghh! I used to know all the lingo - bicycling friend was a dispatcher for the old Chicago Northwestern. I’d go into the office with him sometimes and go over old maps of railbeds. Match them up with existing roads and you’d have a relatively gentile slope for your bike route.
am77494, that’s not really the way ship loading works. Trains of coal arrive and go into a pile, and the other end of the pile goes into a ship. There’s no one-to-one correspondence.
As natural gas has gotten so cheap, coal-powered US power plants have converted or simply shut down. I recently heard a BNSF exec talk about the astonishing drop in coal unit trains moved from the Powder River basin to the Mid-Atlantic region.
What the OP is observing may be due to a change in traffic: where he used to see hoppers of coal moving from Wyoming south through Oklahoma to Texas he’s now seeing hoppers of fracking sand moving north from Texas to North Dakota oilfields. Or as the locos have aged there have been reliability problems and the road superintendent has decided to put additional units on the trains. Most likely, though, BNSF finished lengthening a couple of sidings along the line and now simply has the ability to run longer trains than they used to.
I think part of the reason may also be because they are 2 different trains attached together for a leg of the trip. Something like a combined train runs from point A to B, the the train is split where one part goes from B to C and the other part goes from B to D.
In addition to the answers given above, railroads in recent years have made an effort to increase the average train speed. With the productive economy geared to just-in-time delivery and down-to-the minute dispatching, delivery time has become increasingly important. Applying more horsepower to a train not only enables a higher over-the-road speed, but also allows for more rapid acceleration to reach the optimal speed
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