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Re: china high speed rail

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Fellow Engineers,

High speed trains are wonderful engineering feats, but I don't believe saving energy is one of them. As I recall from my school days: drag force is proportional to speed squared and power (read energy) is proportional to speed cubed. Therefore a train moving at 300 mph, compared to a train at 100 mph,  uses (300/100)^3 = 27 times as much energy.  If the requirement for the number of trains is reduced by 1/3 – to move the same number of people - then the increased energy use is 27/3 = 9. Therefore, 9 times as much energy is required to move the same people/ load with a high speed train as compared to "low" speed train. 

Given a choice, I'll take an airplane.