flatbed vs rail-carriage

flatbed

noun
  • A railway freight car with no sides; a flatcar. 

  • A document scanner with a flat bed. 

  • An open freight vehicle with no sides, designed to carry heavy or outsized loads. 

verb
  • To transport by flatbed. 

adj
  • Having a flat bed. 

rail-carriage

noun
  • A railroad car 

How often have the words flatbed and rail-carriage occurred in a corpus of books? (source: Google Ngram Viewer )