From: stephen@sprunk.org   
      
   On 27-Dec-15 20:32, hancock4@bbs.cpcn.com wrote:   
   > Jishnu Mukerji wrote:   
   >> NORAC signal rules show equivalences between colored light system   
   >> and the Pennsy position light system, which by the way has been   
   >> almost completely superseded by color position light system on the   
   >> NEC. There are multiple ways of indicating which rule applies   
   >> through various signal systems as specified in NORAC.   
   >   
   > I believe much of the Long Island Rail Road and ex PRR SEPTA lines   
   > still use the amber position light signals, though upgrades may have   
   > eliminated some signals.  FWIW, relatively new pictures on nycsubway   
   > of the LIRR trunk line show signal bridges with PRR style signals.   
      
   Most RRs upgrade signals only when they fail, and that won't happen very   
   often for position-light signals; they use long-life, hard-duty bulbs   
   for obvious reasons.   
      
   Also, unlike the transition from incandescents to LEDs, this is a change   
   that really needs to be done for an entire gantry (or set of masts) at   
   once, meaning there's an incentive to just keep replacing failed bulbs   
   individually rather than potentially convert 12+ entire heads.   
      
   OTOH, what all is needed to do a conversion?  Remove the center bulb and   
   block the hole, change two outer lenses from amber to red, two from   
   amber to green, two from amber to lunar white, and then what?  That   
   seems simple (and cheap) enough to just all the rest at once.   
      
   S   
      
   --   
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