Milestones tell more than just a distance; by color of its head,
* National Highway: Milestone Yellow and White color
* State Highway: Milestone Green and White color
* City/District Road: Milestone Blue/Black and White color
* Rural Road: Milestone Red and White color
Also referred as Pradhan-Mantri Gram Sadak
And (Recently I heard about) Asian Highway Network:
How is distance measured between Cities?
Generally, the milestones shows the distance measured between the Head Post Office of the two Cities or Gram-Panchayat office(in case of village) or Center point or Zero Point of the the city decided by ‘Highway Authority’ and ‘The National Survey Bureau’.
One interesting fact, have you heard of Zero Mile of India?
The Zero Mile Stone was erected by the British who used this point to measure all the distances