macadam vs tarmac

macadam

noun
  • The surface of a road consisting of layers of crushed stone (usually tar-coated for modern traffic). 

verb
  • To cover or surface with macadam. 

tarmac

noun
  • The driveable surface of a road. 

  • The area of an airport, other than the runway, where planes park or maneuver. 

  • Tarmacadam. 

  • Any bituminous road surfacing material. 

verb
  • To pave with tarmacadam or a similar material. 

  • To spend time idling on a runway, usually waiting for takeoff clearance. 

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