railroad track vs train track

railroad track

noun
  • A pair of formed steel rails, separated and supported usually on wooden or concrete ties or sleepers, forming a track along which flange-wheeled railroad vehicles may travel. 

train track

noun
  • railroad track, railway track 

  • A set of curves lying in a surface, meeting one another at their respective endpoints in a specific way that resembles railroad tracks 

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