off-ramp vs off-slip

off-ramp

noun
  • A segment of roadway that directs vehicular traffic from a freeway onto local roads. 

  • An exit strategy. 

off-slip

noun
  • A slip road by which traffic leaves a major road such as a motorway. 

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