hard shoulder vs nature strip

hard shoulder

noun
  • A verge to the side of a highway, which should be used only in case of an emergency (especially on a motorway) 

nature strip

noun
  • An area of grass beside a roadway, possibly with a few trees or shrubs, lying between the roadway proper and the footpath, if there is one; a tree lawn. 

How often have the words hard shoulder and nature strip occurred in a corpus of books? (source: Google Ngram Viewer )