slip road vs undertake

slip road

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

undertake

noun
  • The passing of slower traffic on the curbside rather than on the side closest to oncoming traffic. 

verb
  • To commit oneself (to an obligation, activity etc.). 

  • To pass a slower moving vehicle on the curbside rather than on the side closest to oncoming traffic. 

  • To take upon oneself; to start, to embark on (a specific task etc.). 

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