I came across this article on the internet:   
      
   http://vcel.tamu.edu/Other%20Contents/Publications/Hybrid%20Trai   
   %20Power%20with%20Diesel%20Locomotive%20and%20Slug%20Car-Based%2   
   Flywheels%20for%20NOx%20and%20Fuel%20Reduction.pdf   
      
   The authors calculate energy and emissions reductions possible by using hybrid   
   locomotives. They suppose that the consist of locomotives necessary to pull a   
   train up the grades and control it down the grades on a rail line be replaced   
   with a combination    
   of locomotives and slugs with the same total tractive effort and braking   
   power. They further suppose that, instead of chunks of concrete ballast to   
   provide traction for the slugs, each slug is carrying an equivalent weight of   
   flywheel energy storage    
   devices. It then becomes possible to store braking energy to help climb the   
   next upgrade, as well as other energy savings that they describe. I have   
   previously read about a new General Electric locomotive with some on-board   
   energy storage via batteries    
   replacing the normal ballast weight.   
      
   Peter Wezeman   
   anti-social Darwinist   
      
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