mystery tour vs road trip

mystery tour

noun
  • A short-duration outing by coach to a destination that is not revealed in advance 

road trip

noun
  • A recreational or impromptu excursion in a car, usually at long distances from one's home. 

  • A series of games played by a team away from its home field. 

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