rat run vs ring road

rat run

noun
  • A small, usually minor road used by a significant amount of traffic as a short cut or to avoid congestion on more major routes. 

verb
  • To drive through residential streets to avoid congestion on the main roads. 

ring road

noun
  • A circumferential highway around a town, city, or other conurbation. 

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