XPost: uk.railway   
      
   On 28.12.17 14:30, Anna Noyd-Dryver wrote:   
   > Phil Kane  wrote:   
   >> On Wed, 27 Dec 2017 13:12:58 -0000 (UTC), Anna Noyd-Dryver   
   >>  wrote:   
   >>   
   >>> After the old track and sleepers are removed, it appears from that picture   
   >>> that the old ballast is being removed too, following which I would guess   
   >>> that better drainage will be installed, then there's usually a membrane of   
   >>> some kind to keep the sub-soil out of the ballast, this will be followed by   
   >>> the new ballast and finally the new sleepers and rails.   
   >>   
   >> Thank you very much for that explanation of the work to be done.  What   
   >> is not evident to me from the picture is whether the line was on   
   >> elevated structure, on the surface, or underground - the last two   
   >> would entail digging.  I am one-third of the way around the world and   
   >> don't remember those details from my one and only visit to London 50   
   >> years ago!   
   >>   
   >   
   > Even on an elevated structure, replacing the ballast will involve digging!   
   >   
   > This picture posted earlier in the thread   
   >    
   > clearly shows line in a cutting.   
   >   
   >   
   > Anna Noyd-Dryver   
   >   
   >   
   Elevated sections on the New York City Subway don't have ballast, AFAIK,   
   They just run on steel structures.   
      
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