Quite often…at least 50% of the the time on the trains I see here …trains carry only one container in the well with no container on top. If double stacking is so advantageous why does this happen? Why one long train of nonstacked containers instead of a shorter train with containers doubled up?
Clearance issues come to mind.
So does the need to move the cars to where they are needed, as well as air resistance.
Perhaps there are 1 - or more - remaining low-height clearance restrictions on the specific route that is being used by the single-level container trains that precludes running them as double-stacks, which obstructions are obviously not present on the route used by the double-stacked trains. For example, that was the case with NS’ container trains aross its ‘Heartland Corridor’ route until the improved tunnel and bridge clearances were completed last week.
Also, as you probably know, containers do not have uniform heights - they range from 8 ft. for the ISO standard ones to 9’-6’’ for the domestic ones, if I’m not mistaken. A route that can clear a double-stack of ISO containers might not be able to clear a double-stack of domestic ones that are 3 ft. higher overall, so the latter have to go as a single-stack. Is that a difference in the trains you’ve observed ?
Unless all of the trains you see run between the exact same Origin-Destination pairs, that would likely occur on the portion of the route that’s ‘off’ the double-stack routes.
I’ve also seen ‘Special Instructions’ which mandate that double-stacks - or certain combinations of containers - not use a particular track in specified locations, for the same reason. Running as a single-level would give the Dispatcher/ Rail Traffic Controller flexibility to put the train on any track.
What puzzles me is a similar condition that I oberseved on the local NS Reading Line yesterday afternoon - an intermodal train that was a mix of Trailers On Flat Cars (some of which were actually containers on separable chassis as well), single-level contai
It sounds like Ulrich is saying on his line some trains (or even individual cars) are double-stacked and others not. So that seems to rule out clearance questions. So the question remains, why not double stack more and have less waste in hauling only 1/2 loads?
I interpret Ulrich’s question as being on a train vs. train contrast, based on the underlined words.
If so, the reason could be that the single-stack is running over a different route than the double-stacks, at someplace beyond and out of his sight, in either direction. For example, if he’s at or after the junction of one or more lines in a ‘Y’ shape, one of those routes could have a low clearance, and the other route might be able to accomodate the double-stacks.
- Paul North.
Another thing your Forgetting is WEIGHT. You get some fully loaded Max Weight COntainers and your going to exceed the max loading per well even when each truck is rated for 125 tons. A fully loaded 40 footer can weigh over 67K lbs and they do get loaded this heavy and moved in the states like this on the Tridem with Special Permits. Also the 20 footers are heavy also fully loaded. So weight can and is a limit on how they load the wells. Another thing could be the mix of Products you have to watch what your mixing you do not want say Posion Gas near a Flamable or a Food Stuff. So that can restrict were things get loaded.
Sorry…wasn’t clear in my original question. I meant most trains will have double stacks and alot of nondouble stacks…ie. why not shorten the train up by double stacking as much as possible?.. I can speculate on a couple of reasons…but it happens alot, and to me (just a layman observer…no expert)…that looks wasteful as the well cars are expensive specialty equipment used like a simple flatcar…
In a sense it could be considered wasteful that some cars are only “half loaded” or even empty. It is even more wasteful to have some of those cars sitting idle in Chicago and a container being trucked from LA because there were no well cars available on the west coast. In the ideal world there will always be exactly the same number of containers travelling in each direction and the railroads prefer to balance traffic flows if they can. Alas, this is an imperfect world…
Other types of freight cars often travel empty for the same reason - you need to get them back to where the business is being offered. Just as wasteful, and just as necessary.
John
In as much as most stack cars are either 3 wells or 5 wells…the question then becomes are there enough single stacked containers to actually reduce the number of cars. If you have six containers and a 5 well car, you will end up with one well double stacked and 4 wells single stacked. If the car available was a 3 well car, each well would be double stacked.
At loading locations, the normal method of operation is to order X number of feet of empty equipment…no specification is applied as to the need for the cars to be either 3 well or 5 well cars.
Those resaons make sense…if it is for equipment reposition then why load some cars at all? Would it not make more sense to double stack as much as possible and run the surplus equipment empty?.. maybe on the tail end…that way not so much equipment needs to pass under the crane/ through the loading/unloading area…
You can’t always guarantee a 1:1 ratio - 100 containers going east, 100 containters going back west - every train trip. There can be situations where more containers are going one way than the other, at least over a certain period of time. I have seen a train with a long string of empty container well cars, apparently going to someplace that needed some empty cars to load containers on.
Three possible reasons;
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Train handling dynamics, esp. if another loaded block would be added to the tail end, or the empties would somehow become in the middle or front of the train. Better for the loads to be distributed more evenly throughout the train’s length, than concentrated in a few heavier blocks and the empties in a few lighter blocks which might become intermixed.
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The single-level containers can be accessed and unloaded faster and easier than if there is another one on top of them. If they are ‘hot’ or priority loads for some reason, that would be an advantage.
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Time and expense to unload and reload the containers to achieve that seemingly ‘perfect’ uniform consolidation. This may be another instance where random and chaotic chance of an earlier loading process may yield a better overall result that a very rigid operating process.
In the end, i suspect this is just the result of how the train wound up being configured after it was ‘worked’ at its last terminal. If there was no compelling reason to rearrange it - such as the heavy blocks for better train dynamics , or priority loads, etc. - and in view of modern competitive pressures and efficiency drives, the why not just let it go and get it out of town ‘as-is’ ?
- Paul North.
Those are good reasons Paul and you’re probably right… time pressures at loading/unloading probably come into play, especially for for the short hop moves
Time pressure is a biggie. Do you look at what you have to load and then carefully switch cars onto the pad track so loading is optimized or do you set the track with the equipment as it stand off the inbound trains? Most likely, the latter, since you don’t have time and crews to do all that switching. You also might not have a good picture of what you have to load until cut-off - a couple of hours before departure. The containers moving on chassis is not optimal but might be at the bequest of the shipper. Bundling chassis is extra work and has to be done ahead. It also doesn’t work very well if you don’t have the right chassis at the other end to place the box on. You’d have to unbundle the chassis first.