The Efficiency of Trains

By Deane Barker on May 11, 2006

I saw a claim on a banner ad today, and I actually clicked through. It was for a company that makes trains: Norfolk Southern.

The claim is:

Today, we can move a ton of freight an average of 410 miles on just one gallon of diesel fuel.

Uh, wow. I wonder how realistic that number is.

Gadgetopia

Comments

  1. The claim is probably realistic as it doesn’t take a lot of energy to keep an object moving. You need just enough to compensate the friction. The main question is how much fuel is needed to accelerate a ton of freight to a speed of 410 miles.

  2. Eh, I wouldn’t say it’s too far off the mark. Pretty realistic actually.

    Figure a 3000-pound TDI Volkswagen will get maybe 50 miles per gallon in mixed highway driving. Your biggest losses occur from:

    1) accel and decel (not staying at steady state) 2) wind and road resistance 3) internal inefficiency 4) no regeneration

    A train neatly solves all these things. Aerodynamically, in terms of frontal area and wind resistance, a train has the advantage of being able to exponentially increase its length and mass without significantly increasing its drag. True, you’ve got an acceleration period at the beginning of a train route, but at the same time, stopping on the end of the route is a regenerative process, and in the case of diesel-electric trains a lot of the stopping power comes solely from regeneration into the batteries. Once the train is at speed, it will remain there for hundreds or thousands of miles, which allows the engine to be greatly optimized for that one speed. Then you’ve got steel-on-steel rolling friction, which is an order of magnitude less than rubber-on-asphalt, plus extremely efficient bearings and spindles.

    Think of it like that, and basically what you’ve got is a very idealized version of long-distance transportation. The main problem that we’re left with is the infrastructure: it’s still not as convenient to place an item on a train as it is to just drive the same item to its exact destination. I think with rising fuel costs though we’ll see an increase in the effort put forth to integrate rail transport more effectively into our shipping system.

  3. Jeroen: I think the real question is:

    “How long must the entire journey be in order to being the average up to 410 miles?”

    Pro’lly at least cross-country (USA) … or maybe cross-continent (Asia -> Europe)?

  4. I’d like to amend my previous post – guess the coffee hadn’t quite kicked in yet – but diesel-electric trains don’t regenerate into batteries as I originally said. Pure electric trains will sometimes do this, and in other cases they’ll actually put power back into the grid, but diesel-electrics just dissipate the regenerated energy as heat. It’s used to provide braking power but that’s about it.

    Now I’m curious as to whether that 410 mile figure is a true average or just a ‘peak’ after steady state is reached. Looks like I’ve got something to research now when I have some downtime.

  5. I’m guessing that this is a differential cost. In other words, an additional ton of freight added to an existing train uses an extra gallon of fuel over 410 miles. It’s the fixed costs that eat you up.

  6. I think Brenda has it. Imagine a train with one hundred boxcars. Now add one additional ton to the last car. What cost would that incur? But there is another factor. It just seems intuitional that rail freight would cost less than shipping by truck. A boxcar is about the size of an 18 wheeler. So compare a train of one hundred boxcars driven by a three person crew with 100 individual trucks driven by sometimes two drivers each. Consider, too, that the truck must pay the same price for diesel as you do for your diesel powered Mercedes, where the railroads probably fill up from tanker trucks driven straight from the refinery that probably gives the railroad a steep discount.

    So why do most companies ship their goods by truck? Well, after drinking my personal blend of scotch and thinking about this, it dawned on me that the railroad owner has to build and maintain the roadway, and that must be a very expensive surcharge on the freight they haul. On the other hand, we tax payers provide the roadways for the trucking companies – a freight surcharge that we pay, not the person who receives the freight.!!! What a deal for the trucking companies, huh!

    PS: Want to know my personal scotch blend? 200 milliliters of very expensive Laphroaig Single Islay Malt Scotch (the smokiest of all) mixed into about 1.5 liters of very cheap Inver House Scotch. The resulting product is very much better than Dewar’s White Label Scotch.

  7. Stephen makes a good point.

    I did some more figuring over the weekend, and I’m not as impressed anymore. An average tractor trailer carries 45,000 pounds (22.5 tons), and gets roughly 7-8 mpg. Using that figure provided by Norfolk Southern, this works out to be 18 mpg for a train moving the equivalent amount of freight. So granted, compared solely weight-to-weight with a VW TDI automobile, the train seems great…but after considering the economy of scale it’s really not as huge an improvement as that sounds.

  8. Not to pick on minutia, but there’s actually a flaw in the original post – Norfolk Southern does not “make trains”. They are a rail-based transportation and logistics company. They “use trains”.

    As for why companies use trucks “more than” trains – the answer is typically time and volume. To ship something coast-to-coast via truck can take as little as 3 days. By train it can take 7-10 days. In the age of quick consumer demand and just-in-time industry, the train doesn’t work for most everyday consumer-related goods. It has the potential too, but that would require additional investment by both the companies and rail lines.

  9. This from the website of CSX (another rail transport company):

    Railroads now move a ton of freight nearly 410 miles for each gallon of diesel fuel used, up from 235 miles in 1980 and 332 miles in 1990. A truck, on average, moves a ton of freight about 100 miles for each gallon of diesel fuel.

  10. I had a similar argument this morning over which is the more effecient: train or plane. My friend argues that a plane is more fuel effecient (which I doubt).

    Secondly, why is a plane ticket much cheaper than a rail ticket for the same distance? Is it fuel or maintenance of the tracks that bumps up the costs or just that the rail companies are greedy?

  11. I don’t think the rail companies are greedy, but the cost of mantaining track really does up the price. And also a train makes a lot more stops than an airplane. A train from Santa Barbara, Ca. to Los Angeles Ca. takes 7 hours, but an airplane only takes half an hour.

  12. its 95 miles from Santa Barbra to LAX. They actually fly planes between the two? I think the cheap seats come from the amount of major stops you can get from a plane per day. 4 or 5 major airports in a day isn’t hard, much easier for you keep that plane regional to the north east, or south east. A train will only make 2 or 3 stops a day if it is used in regional service, and there are few rail hubs. There is only 1 real long distance passenger rail service left. It loses money almost every year, but by law isn’t allowed to go out of business. Its strictly the number of passengers moved, that makes the difference. A train moving 1 passenger car, costs about as much to operate as a train moving 10. The problem is, that people moved to airlines for speed, and the trains had to raise rates. Now that rates are high, its hard to move back.

    I dont know why that 95 mile trip takes 7 hours, but it sounds like you have to make connections or something, and will be sitting at a station for 5 hours.

  13. Another point to make is this: Trains utilize a very efficient diesel motor, turning at a single speed, to power a much larger alternator. But when the batteries powering the electric motors on the wheels are charged, the train’s computer can turn off the combustion engine without stopping the movement of the train itself. The combustion engine may run for a very small fraction of the amount of time it takes to go 400+ miles, thus generating a high mpg rating. To truly see how much energy is being used (and it’s total costs), you must also determine the number of kilowatt hours being consumed by the motor for the full length of the trip. Now multiply by the price per kilowatt hour of electricity, and you’ll have a true cost of powering the train.

  14. Now multiply by the price per kilowatt hour of electricity, and you’ll have a true cost of powering the train.

    I don’t know if that’s true though. Since the batteries powering the wheels are charged by the diesel engine (as opposed to being pre-charged from the grid, for instance), then the only thing consuming fuel in the end is the engine.

    I guess I don’t care about the batteries powering the wheels. They’re free, in a way. The cost is borne by the engine, so all I care is how much that consumes. How it gets its power down to the wheels is irrelevant from a efficiency perspective.

  15. a ton of feather will cost more to trnaport than a ton of coal…density is th number one concern here. The claim does not address number of cars, aerodynamics and grade. A ton of feather occupies more space than a ton of coal..and passenger rail is very inefficent.

  16. trains are more efficent than trucks, 1 locomotive carring 6,000 tons would take over 250 semi trucks to move the same load.

  17. In regards to the price of plane tickets cpmpaored to rail. Airlines are like the truckin industry Cut throat an airline would let itself male A loss on LAX Santa barbra run to male The money back elsewhere , unlike rail few companie. As well as passenger trains take up a slot in the timetable That a freight train could use so it comes down to clear profit and priority

  18. I just wanted to say thank you to all of those people out there–particularly Deane and Chris–for actually showing interest in such an important subject that most common-folk would ignore in belief that they couldn’t do anything to change it. I am 12 years old and am on a LEGO robotics team, and we are studying the efficiency of trains, which apparently is a very wide-range subject. You guys have helped me a lot. :)

  19. It’s not just the fuel economy, is taking these big trucks off the highway. They slow traffic down, cause accidents, polute the air. There is more to trains than just fuel economy.

  20. can we turn of diesel engine? i herd that it cant be turned off is it true?plz give information about it

  21. Diesel electric trains are not ‘hybrids’ and they don’t shut off the engine. In fact, starting up and shutting down the engine is an involved process that takes several minutes at least to complete. That’s not of you count all the prep work leading up to firing up the engine.

    There are no batteries aside from the batteries used to start the engine. The engine generates the amount of power needed to keep the train moving and thats it. Hybrids make efficient use of stop and go but are inefficient with long constant speeds, so in a train it wouldn’t be practical. There is “regenerative braking” but that’s simply to save the brakes. The power created is sent to a giant heating element (the most inefficient use of electricity, therefore it can consume alot and make the brakes work well) and a fan to cool that heating element. This is called the “dynamic brake”.

    Steel on steel is the key to a trains efficiency. They are far and away the most efficient way to move a large amount of freight. On a flat ground, if you were to shut a train off, it would continue to roll for miles and miles, only slowly losing speed and the majority of that being due to wind resistance. The rubber-on-asphalt of a truck will cause it to slow down to nothing in a very short time.

    Acceleration is its only real hit. They don’t accelerate slowly because they are too heavy, they accelerate slowly because if you don’t, their wheels will spin on the track and won’t get traction. In fact, when starting up a hill, trains blow sand on the track to give them a little grip.

    Finally, airplanes are not more efficient than trains, but the large customer base of airline passengers allows them to make more efficient use of their transit. They can fill a plane up, whereas passenger trains struggle to fill a few cars, all being pulled by a vehicle that’s designed to pull hundreds of times more weight. So therein lies the problem, it’s kind of like driving a tractor trailer to work. Its less efficient than air because they can’t fill it up. Fill it up, and it will be expoentially more efficient than air. Otherwise, we’d ship all that freight by air!

  22. In addition semis cause a lot of wear to our transportation infrastructure. If transportation companies started to use more trains to transport with a combination of semis the overall cost of transporting goods would decrease.

    One of the major reasons for the initial loss of trains and increase of semis was due to fuel efficiency not being a major issue several decades ago. As a result of the decrease in the trains needed, many railway companies pulled up their tracks. Now to rebuild the tracks would be very time consuming, expensive, and labor intensive. But if transportation companies were to go this route, they would be much more profitable in the end.

    An interesting fact about this is that the infrastructure in the united states was built to last about 40 years, and 80% of of all infrastructure needs replacing. This is a major concern of our government right now. President Obama stated himself that as a county we need to get semis off the roads the use a more efficient means of transporting goods. I do realize that not all products would be able to be transported by train, but I know that there are many that could be. I feel this is a direction that we need to move in as a country.

  23. I stumbled across this post, and I can’t help but to chip in a little after reading all the comments. (You guys are thinking about

    this so intently, with things that I agree and disagree.)

    <I guess I don’t care about the batteries powering the wheels. They’re free, in a way. The cost is borne by the engine, so all I

    care is how much that consumes. How it gets its power down to the wheels is irrelevant from a efficiency perspective.>

    You really should care about it, mainly because it affects how much energy is being recovered/how much energy is being used at

    the steady state (which can be long for a 24 -48hr total transit time). But I get your point; you just want the average figure, which

    is ok since that empirical figure will be very realistic to what you actually get out of your fuel. But if you look at the question

    qualitatively, and for the purpose of further improving efficiency, you will need to look into the science and statistics behind the

    empirical data.

    You should add “not all” in front of it. There are hybrid locomotives that basically do the battery thing as their automotive counterparts do. There are also hybrid locomotives that basically is a combination of truck engines that are computer controlled and are able to start/shut off themselves depending on the amount of power needed to be delivered. While most of these locomotives are not currently in mainstream long haul fleets in north America, the green initiative in recent years has prompted a lot of big players to look into doing that, including GE Transportation.

    My personal note to train efficiency and passenger transportation using trains is, use the appropriate tool for the appropriate job. If you are needing flexibility, automotives are the way to go. But if you are needing capacity in terms of weight or quantity, trains are the way to go.

    I hear too may people commenting trains are inefficient for passenger transport. However, one really need to understand that the problem lies not in trains are not efficient, but rather, it is the current infrastructure supports and favor automotives and trucks in north America. Cities are spread out in a very significant and unhealthy way (in terms of energy efficiency) due to historical reasons, which does not support the efficient use of trains as a tool – which is great for hub-to-hub transport but not the point-to-point transportation model. If you look at other countries that utilize trains for transportation a lot, their urban centers tend to be much more condensed that those in north America, which increases the amount of traffic on a particular route to make it a viable and profitable option to run trains instead of vehicles/airplanes.

    I personally support revitalizing inner city areas and condensing cities to become higher density communities. Not only does it reduces the amount of energy usage in transportation, but it also translates to less time lost in driving and higher net productivity. Commercial activity will also see a significant increase in city areas, which is a plus to a lot of business owners. However, there is already too much money spent on the current way cities are being developed. It will be nearly impossible for north Americans to change that unless a catastrophic event wipes out a city and people have to rebuild it from scratch.

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