checkpoint vs traffic jam

checkpoint

noun
  • A point or place where a check is performed, especially a point along a road or on a frontier where travellers are stopped for inspection 

  • A predetermined point in a map, level or scenario that the player may resume from if they die or restart from if they choose to. 

  • A situation, often represented by a point in time, at which the state of a database system is known to be valid, and to which it can be returned in the event of a crisis by using a combination of backups and logs; the data stored at this event. 

verb
  • To set a checkpoint. 

traffic jam

noun
  • A situation in which road traffic accumulates until it is stationary or very slow. 

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