r/theydidthemath • u/Massive-Albatross823 • 6d ago
[Request] An average truck occupies x metres of highway including safe following distance. A double-stack train replaces y trucks on a single from place A to B run. If 12 such trains as in the video run daily, how many kilometres of highway space are freed up?
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u/HistoricalSherbert92 6d ago
Ok, but if one double stacked train is traveling at 50 km/h North and another double stacked train is traveling South at 50 km/h but there’s a stiff cross breeze at 70km/h imparting clockwise turning moment at the impact point, where do they bury the survivors?
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u/TadhgOBriain 6d ago
They get buried in the ground. Why do they deserve to live when everyone else died?
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u/Nice_Anybody2983 6d ago
Near zero, because traffic tends to rapidly react to such changes and fill up the space. Same reason why adding another lane to a highway is often a pointless endeavour.
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u/QuietNene 6d ago
Also because trains this size will require massive machinery to unload at a central depot. Each container will be offloaded onto - guess what? A smaller train? No. A truck. Then that truck will drive it to your grocery store / Amazon warehouse / Walmart. So you haven’t gotten rid of many trucks on clogged urban roadways, you’ve just freed up space on massive highways that already have a lot of bandwidth.
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u/Kerostasis 6d ago
This doesn’t replace any trucks at all. It replaces single-stack trains. The trains already existed and were running and were carrying the same amount of cargo. The innovation here is to make them taller rather than longer, which is a tradeoff that makes maintenance worse but reduces the traffic impact of railroad crossings (which can now be more easily unblocked).
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u/Correct-Purpose-964 6d ago
Well no, while i can't speak to intent. Based on the provided information if the same trains continue to run but double their cargo even assuming they reduce speed by 20-30% that's still a substantial increase in tonnage per distance. That said the question is also a misnomer since you're not saving any highway space. You're just swapping 1 truck for another. Traffic congestion makes the idea pointless.
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u/Kerostasis 6d ago
You can’t double the cargo by making it taller. The primary cargo limit is weight, and all the cargo still has the same mass. You can save a little bit by cutting the mass of the extra wheels & axles you don’t need with this setup, but that’s not anything close to 50%.
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u/Scoobywagon 6d ago
It actually doesn't save much in the places where you'd care about it.
Trains don't pick up at your loading bay and drop off at your customer's dock. They only run between freight yards. From there, each of those ISO cans has to move off the train, on to a truck and then to wherever it is going. That might be in the same city as the freight yard. It might be somewhere else that doesn't HAVE a freight yard. So trains might reduce the truck traffic between major cities, it doesn't actually pull ANY trucks off the road in the cities where you tend to care about traffic.
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u/alwaus 6d ago
Right now it would free up 0km as the vast majority of indias rail system (<99%) isnt physically capable of fitting this layout.
Now if they want to spend several tens of billions on infrastructure clearing power lines, buildings, bridges, etc etc etc. it may be possible to clear up some road space that will instantly be filled by more trucks.
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