elevated railway vs train track

elevated railway

noun
  • a rapid transit railway with the tracks above street level on a viaduct or other elevated structure 

train track

noun
  • railroad track, railway track 

  • A set of curves lying in a surface, meeting one another at their respective endpoints in a specific way that resembles railroad tracks 

How often have the words elevated railway and train track occurred in a corpus of books? (source: Google Ngram Viewer )