dual carriageway vs high road

dual carriageway

noun
  • A road in which the two directions of traffic are separated by a central barrier or strip of land, known as a central reservation or median. 

high road

noun
  • A main road or highway. 

  • Used other than figuratively or idiomatically: see high, road. 

  • A course of action which is dignified, honourable, or respectable. 

How often have the words dual carriageway and high road occurred in a corpus of books? (source: Google Ngram Viewer )