On Thursday, June 19, 2014 12:44:20 PM UTC-4, Adam H. Kerman wrote:   
      
   > I don't quite agree with your mathematical analysis there, Stephen.   
   > Within certain ranges of excessive speed, lighter rolling stock can   
   > bounce more than heavier rolling stock, INCREASING derailment risk,   
   > whereas in other ranges, it's possible for lighter to have a lower   
   > derailment risk than heavier. With regard to poor track, it depends on   
   > what maintenance is required and I suppose a bit of luck, so don't   
   > make any general statements, George.   
      
   A "light weight" train is still quite heavy.  A train's actual weight isn't as   
   important as the truck design, the suspension system, and weight distribution.   
      
   We had an automobile that handled very poorly.  It wasn't that the car was   
   light, but rather its crappy suspension.  Our next car was even lighter, but   
   rode much better thanks to a better suspension.   
      
   NYC subway cars were once very heavy, but on bad track still rode like crap.     
   Thanks to better truck design, modern light weight cars will rode smoother   
   than the old heavy weight tanks.   
      
   Phila's light MFSE Budd cars rode like crap.  But when they were re-trucked   
   for use on the P&W, their ride was very smooth.  It wasn't the light weight,   
   but a better truck.   
      
   You mention PCC cars.  Some cars on some lines rode poorly, but that was due   
   to the PCC truck design being optimized for smooth welded rail in city street   
   service; the trucks did poorly on jointed rail and rural track.  An improved   
   truck rode better.  (   
   Also, the CTA PCC L cars were a heavier design than PCCs built for street   
   service.)   
      
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