bollard vs traffic island

bollard

noun
  • A similar post preventing vehicle access to a pedestrian area, to delineate traffic lanes, or used for security purposes. 

  • A strong vertical post of timber or iron, fixed to the ground and/or on the deck of a ship, to which the ship's mooring lines etc are secured. 

traffic island

noun
  • A raised area in a roadway or traffic circle, bordered by curbs, used to control traffic. 

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