From: ahk@chinet.com   
      
   Stephen Sprunk  wrote:   
   >On 19-Jun-14 01:59, Glen Labah wrote:   
      
   >>There are other countries out there that have fewer derailments than   
   >>the USA.  It seems to me it might be worth taking a look at some of   
   >>those countries to see what they are doing that is different.   
      
   >For one thing, they're using significantly lighter rolling stock, which   
   >lowers the risk of derailment due to excessive speed or poor track.   
      
   >The FRA weight penalty strikes again...   
      
   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.   
      
   I can tell you that heavier has an advantage over lighter over rough   
   track (not track in need of immediate maintenance) in terms of giving   
   the passenger a better ride, without relying on ideal suspension systems.   
   PCCs bounced like crazy on the "L", especially on the south side in which   
   CTA performed a botched tie replacement job in the mid '70's that led to   
   years of slow zones in the '80's. I'm not old enough to have ridden the   
   4000s in regular service, but in special movements, they've always ridden   
   smooth as glass over poor track. PCCs were based on light weight street   
   cars of the 1930's and 4000s were based on heavyweight intercity cars   
   for steam roads.   
      
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