express train vs flat out

express train

noun
  • A train (either the service or the train itself) making limited stops. 

flat out

noun
  • A uncambered corner of racetrack; a racetrack whose corners are uncambered. 

  • A wrap, an item of food consisting of various ingredients wrapped in a tortilla or pancake. 

  • A section of piste that is relatively flat, causing or allowing skiers to slow down. 

  • A baked portion of flatbread; a baked item that is not meant to rise. 

verb
  • To fail after a promising beginning; to disappoint expectations. 

adj
  • Complete, total, downright. 

  • Lazy, sleeping. 

  • Very busy. 

  • Used other than figuratively or idiomatically: see flat, out. 

adv
  • At top speed. 

  • Bluntly, no holds barred, totally, outright. 

How often have the words express train and flat out occurred in a corpus of books? (source: Google Ngram Viewer )