motorway vs neutral ground

motorway

noun
  • A highway with grade-separated crossings (rather than level crossings) and designed (and only permitted) for high-speed motor-traffic (in Europe motor vehicles with a higher speed limit than 40 km/h) running in two directions on one separate carriageway each 

  • A racetrack venue designated especially for the sport of auto racing. 

neutral ground

noun
  • The median strip or central reservation between lanes of traffic in a divided highway. 

  • Used other than figuratively or idiomatically: see neutral, ground. 

How often have the words motorway and neutral ground occurred in a corpus of books? (source: Google Ngram Viewer )