bollard vs milepost

bollard

noun
  • A similar post preventing vehicle access to a pedestrian area, to delineate traffic lanes, or used for security purposes. 

  • A strong vertical post of timber or iron, fixed to the ground and/or on the deck of a ship, to which the ship's mooring lines etc are secured. 

milepost

noun
  • A post on a highway, often with one or more fingerposts, showing the distance in miles to nearby places 

  • A sign or post beside a railway marking the distance from the (actual or nominal) start of a line (usually the principal terminus or junction with a more major line) 

verb
  • To place mileposts along (a road, etc.). 

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