Wiktionary
rat run
n. (context idiomatic English) A small, usually minor road used by a significant amount of traffic as a short cut or to avoid congestion on more major routes. vb. (context idiomatic English) To drive through residential streets to avoid congestion on the main roads.
Usage examples of "rat run".
But I think the view of Hamnpork in possession of all the facts will be a little different than the view of Hamnpork who just shouted because he saw a rat run away, hmm?