Mexican standoff vs head-on collision

Mexican standoff

noun
  • A near-collision between two trains; an averted cornfield meet. 

  • A pot that is split among the players because of a tie. 

  • An inconclusive standoff, ending in mutual retreat. 

  • A confrontation among two or more armed parties, none of which wants to attack first (fearing that the other could retaliate), but neither of which will disarm (for fear the other will attack). 

  • A stalemate, or a confrontation among two or more sides that no side can win. 

  • A three-way or more standoff. 

head-on collision

noun
  • A collision where the front ends of two vehicles (such as ships, trains, cars, planes, etc.) hit each other, as opposed to a side-collision or rear-end collision. 

How often have the words Mexican standoff and head-on collision occurred in a corpus of books? (source: Google Ngram Viewer )