expressway vs subway

expressway

noun
  • A road built to freeway standards. 

  • A divided highway, especially one whose intersections and direct access to adjacent properties have been eliminated. 

  • A road built for high speed traffic, but not up to motorway standards or designated a motorway. 

subway

noun
  • An underground route for pipes, sewers, etc. 

  • A rapid transit system, regardless of the elevation of its right of way; a metro system. 

  • An underground railway, especially for mass transit of people in urban areas. 

  • A train that runs on such an underground railway. 

  • An underground walkway, tunnel for pedestrians (called pedestrian underpass in US). 

verb
  • To travel by underground railway. 

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