From: r.m.ellsworth@att.net   
      
   Overmod (Robert M. Ellsworth) wrote:   
      
   > > https://www.scribd.com/doc/241718975/NYC-Tunnels-Assessment-Report   
      
   Stephen Sprunk wrote:   
      
   > Not interested in giving them a bunch of personal information just to   
   > read what _should_ be a public document.   
      
   Very true, but the document is marked as being 'confidential' and I suspect   
   you will not find it Web-available in accessible form otherwise.  If you   
   e-mail me I can attach a copy of the .pdf.   
      
   Top-down track is aligned using the contact area of the railheads as the   
   alignment data, rather than working from the bed upward.  It's pretty common   
   design practice for Class 9 track construction.  Here is a reference   
   (downloadable .pdf, FRA Research    
   Report RR-08-03 from July 2008) that references top-down construction with   
   respect to slab track:   
      
   ntl.bts.gov/lib/42000/42800/42879/rr0803.pdf   
      
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