main road vs national road

main road

noun
  • priority road; A road with entering traffic which must yield right of way 

  • High Street; Main Street 

  • A major road in a town or village, or in a country area. 

  • A major urban road, off which lead many smaller streets, many of them cul-de-sacs. 

national road

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