roadway vs underground railway

roadway

noun
  • The portion of a bridge or railway used by traffic. 

  • The main or central portion of a road, used by the vehicles. 

  • A way used as a road. 

underground railway

noun
  • Synonym of subway: a railway under the ground. 

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