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Reverse traffic pyramid
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this post was submitted on 08 Feb 2026
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Nice. I've looked into this question fairly deeply and this seems fairly accurate.
Two things that people find counter-intuitive (or in the second case prefer not to think about):
Are you sure? Where I live all high-speed trains are running on 100% renewable electricity, while intercity buses run on diesel. Also multiple carriages at the same time, traveling on rails, should be significantly more efficient than a single bus traveling on asphalt. I agree that there will be an increase in energy expenditure depending on speed, but it shouldn't be as significant as the combination of the other two.
We would have to make it sustainable eventually, since it's the only practical way for passengers to travel between americas/australia/afroeurasia. I guess something hydrogen-based is the most likely candidate for reducing the carbon impact.
Hoovering and hydrofoils have been under-explored, but yes, speed is necessary for long-distance travel.
Irrelevant to what I said: discounting energy source.
Trains obviously have much less rolling resistance, as you say (an advantage partly offset by their added weight). But wind resistance is the bigger factor, and trains are usually just faster.
A train travelling at 350kmh uses 40% more energy than one going at 300kmh. This is why the service speeds usually top out at 300 everywhere, Europe, japan and China.
Speed really is the decisive factor. The pyramid hints quite well at this.
But we can't really discount the energy source. An intercity bus service running fully on renewables is not feasible neither now nor for the foreseeable future. What we should do is have more efficient rail service between city, with more slower and cheaper options for when you don't mind the extra hour on your train.
Defining "green" as energy consumption is quite exotic. More commonly it has to do with resource (carbon and others) footprint.
Compared to cars? Or just trains?
Compared to everything.
You're telling me that 140 people driving from New York to California is more efficient than 140 people taking a single 737?
If they share 35 cars, yes.
If they each drive their own cars, no, it's close, and depends on what cars they drive.
Shared rides is a step above on the pyramid.
From what I can tell it's not really close. At least for "average cars" and "typical commercial airlines".
https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft
Now take into account that CO2 released at altitude is twice as bad as on the ground, since it absorbs all sunlight before part of it gets filtered out by the atmosphere or reflected by clouds.
I hardly think that's relevant. CO2 doesn't stay where it was released.
https://airs.jpl.nasa.gov/resources/107/concentration-of-atmospheric-carbon-dioxide-from-earths-mid-troposphere-2002-to-2013/
We're talking about yearly averages and decades of warming. Days to weeks is very short by comparison.
You're right, I misremembered. It's not the CO2 that has a higher effect when released at altitude than on the ground.
It's Nitrogen Oxides, water vapor and soot.
"In 1999, the IPCC estimated aviation's radiative forcing in 1992 to be 2.7 (2 to 4) times that of CO2 alone − excluding the potential effect of cirrus cloud enhancement.[6] This was updated for 2000, with aviation's radiative forcing estimated at 47.8 mW/m2, 1.9 times the effect of CO2 emissions alone, 25.3 mW/m2.[7]"
https://en.wikipedia.org/wiki/Environmental_impact_of_aviation#Factors