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I was floored to recently discover that trains get only about 43 MPG per passenger -- worse than a Prius (46 MPG). And of course, if you put two people in the Prius, then the Prius MPG doubles. Heck, you could put two people in a 22 MPG car and then do better than the train.
It seems there are two reasons for trains' poor performance. First, they're often heavier than cars on a per-passenger basis, so they take almost as much fuel to run. (Not quite as much, since there's some efficiency from running on a fixed track vs. a road.) Second, there are usually lots of empty seats.
This doesn't mean that people should feel justified taking their car instead of the train just because the reported MPG is similar. That's because if they take their car they're definitely burning a lot of extra fuel, while the energy of the train is practically "free" because it's going anyway. And of course, there are 100 other reasons why trains are better than cars for the environment and for society.
Still, it's kind of a frightening thought that if we replaced all current passenger train trips with high-MPG car trips, the energy use could be similar. I thought trains were supposed to save us, not Priuses.
By the way, highway buses are reported to get 148 pMPG, and several sources give about 48 pMPG for airplanes. Here are sources for trains:
Wikipedia. 33pMPG for cars, 41pMPG for transit rail -- and cars' figures will get better as people keep ditching SUVs
U.S. Passenger-Miles Per Gallon. 45 pMPG for Amtrak. Incredibly detailed monograph by David Lawyer.
Vermont Rail Advocacy. Says that Amtrak uses 21% less energy than cars. Cars thus break even once fuel efficiency goes from the current 22 MPG to just 27 MPG.
Rail vs. Auto Energy Efficiency. Another detailed article by David Lawyer.
Energy efficiency of different modes of transportation, by James Strickland. He gives much higher figures for train MPG, but I think he might be using higher-than-average train capacities.
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Unless there is a global financial / social meltdown the private use of the automobile is not going away anytime soon. In Texas we have the most inefficient use of resources on the planet so we have more room to keep the autos on the road with minor adjustments in efficiency. New York city recently made changes in their development codes to allow for more parking in downtown New York. The car is not going away it is going to get smaller and more efficient.
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What trains are these? Our European friends were here, and when they saw the Amtrak train, their response was "Oh, how quaint--like the trains we used to ride when we were young!" Maybe our trains aren't the most efficient because they are older design.
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Okay, Chavela, good point -- American trains are likely less efficient than those elsewhere, because everything in America is less efficient. In this case, the culprit is probably not enough passengers. By contrast, in Japan the trains run lots of passengers all day and all night, not just during rush hour. David Lawyer says Japan rail travel is "a few times" more efficient. If by "a few times" we assume 3x, then suddenly trains are way in the lead. Wikipedia says Japan trains use 0.35 MJ per passenger kilometer, which works out to 235 pMPG! Maybe they're overestimating somehow, but even if they were off by a whopping 50%, then their trains are still about 3x more efficient than ours.
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Full light rail trains do very well on efficiency - and this is from a guy who now owns TWO Priuses. To say nothing of the fact that the Prius usually has only one person in it as well.
Also, electrified rail can be run off a much larger array of power sources than can rubber-tired vehicles. The Prius can't be charged by electricity, and someday down the road when its successor can be, the efficiency will be less than for a train run by overhead wires due to losses inherent in batteries.
Last edited by m1ek (2008-09-22 15:33:12)
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You can't beat steel to steel for keeping down on road resistance.
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And most of the energy used for a car is pushing the air away: which goes right back into place for the next auto to push away.
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And most of the energy used for a car is pushing the air away: which goes right back into place for the next auto to push away.
Not to be confused with a bike, where most of the energy used is used to push the air away: which goes right back into place for the next bike to push away.
For a train, a lot of the energy is probably used to push the air away: which goes right back into place for the next train to push away, though of course a lot goes into rolling friction on the track. I don't know what the ratio between the two is. In any event, as I understand it, the rolling friction experienced by trains on train tracks is about 1/10th as much as it would be with rubber pneumatic tires (which is basically what you just said.)
Done properly, a train should be much more efficient (i.e. moving X lbs of cargo or people to a point Y miles away, with the efficiency being (X * Y / energy required)) than a car. But of course, it's not always done properly.
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It really doesn't make much of a difference how little rolling resistence a train has. They are just so massively heavy that they require enormous amounts of power to get moving. I always wondered why passenger trains had to be so heavy? Is it neccessary for each car to weight 100,000-200,000 lbs?
And especially when you consider that most trains don't use regenerative braking technology, I don't know how anyone could consider a train as efficient.
I see much room for improvement, but then again, I'm not a professional engineer.
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