dual carriageway vs parkway

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. 

parkway

noun
  • A divided highway with a landscaped median. 

  • A scenic freeway. 

  • A tree lawn. 

  • a railway station built on the edge of a town, typically with a large car park to function as a park and ride interchange. 

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