road vs slip road

road

noun
  • A way used for travelling between places, originally one wide enough to allow foot passengers and horses to travel, now (US) usually one surfaced with asphalt or concrete and designed to accommodate many vehicles travelling in both directions. In the UK both senses are heard: a country road is the same as a country lane. 

  • A partly sheltered area of water near a shore in which vessels may ride at anchor; a roadstead. 

  • A railway or (UK, rail transport) a single railway track. 

  • A path chosen in life or career. 

  • A way or route. 

  • Roads in general as a means of travel, especially by motor vehicle. 

  • An underground tunnel in a mine. 

adj
  • At the venue of the opposing team or competitor; on the road. 

slip road

noun
  • A segment of roadway that joins a motorway to ordinary roads (in either direction) 

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