From: ahk@chinet.com   
      
   Overmod (Robert M. Ellsworth)  wrote:   
      
   >>>What does "top-down track system" mean?   
      
   >>In direct fixation, it means top of rail and gauge are established to the   
   >>specification, then the fasteners are attached, then the concrete is placed   
   >>last. That really makes a lot of sense, because there's just the one step   
   >>at which things are calibrated. Bottom up requires a lot more calibration.   
      
   >In connection with direct fixation, you might enjoy some of the   
   >references on the GERB company's Web site:   
      
   >http://www.gerb.com/en/arbeitsgebiete/arbeitsgebiete.php?ID=107&kategorie=5   
      
   >Note the 'sidebar' at top right with some technical descriptions of the   
   >instantiations.  This is more than just direct fixation, but I think it   
   >is significant if the track is to be used for effective high speed.   
      
   >(The Germans have a long and fascinating history with sprung track...)   
      
   Yeah, I encountered serveral references to one of the variations,   
   floating slab, but didn't quite understand it. This site helps. Thanks.   
      
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