main drag vs slip road

main drag

noun
  • The main street of a town or suburb, or the principal highway passing through a rural area. 

  • Used other than figuratively or idiomatically: see main, drag. 

slip road

noun
  • A segment of roadway that joins a motorway to ordinary roads (in either direction) 

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