how about turbine-tunnels in the tube? Those trains always seem to push along a howling gale!
Reminds me of the atmospheric railway from very long ago, remnants at Crystal Palace. It was a train in a tunnel with leather sealing rings between train and tunnel. Air was pumped into the tunnel to push the train though like a bullet in a rifle barrel. You won't be surprised to know it wasn't a success.
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We're a creative & practical bunch here, aren't we?! 
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