cross-member vs railway line

cross-member

noun
  • A beam lying crosswise; a rail. 

railway line

noun
  • A railway track; a pair of rails on which a railway train runs. 

  • A group of railway tracks running parallel, allowing one track to be used for each direction (a double-track railway line), or allowing segregation of fast trains from stopping trains (a four-track railway line). 

  • An organization that runs a railroad. 

How often have the words cross-member and railway line occurred in a corpus of books? (source: Google Ngram Viewer )