double-decker vs passenger train

double-decker

noun
  • A vehicle (usually a bus, coach or train) or aircraft with two floors. 

  • Any object with two layers or parts stacked on top of each other. 

  • A sandwich with three slices of bread, whose toppings are on both sides of the middle slice. 

  • A headline that is two lines long. 

  • a man who both penetrates (top) and is penetrated (bottom) in sex with other men; sometimes also has relationships with women and/or presents masculine as well as feminine mannerisms and appearances. 

  • A frigate with two decks above the waterline. 

passenger train

noun
  • A train whose primary function is to carry passengers. 

How often have the words double-decker and passenger train occurred in a corpus of books? (source: Google Ngram Viewer )