Significant of national highways

It links extreme part of country. 
National Highways are the grade roads that connect every major city of India and are the backbone of the road infrastructure. 
National Highways constitute only about 1.7% of the road network but carry about 40% of the total road traffic.
The Indian roadways network ranks as the second biggest roadways network in the world.
The density of the highway network of India is somewhat more as compared to the United States (0.65) 

1.The national highways network of india is a network of trunk road that is managed and maintained by CPWD, Central Public Works Department, an agency of government of India. 
2.The National Highway Authority of India(NHAI) is the nodal agency responsible for building, upgrading and maintaining most of the national highways network. 
3.India has 111,111 km (69,041 mi) of national highways (NH) connecting all the major cities and state capitals as of March 2018.
4. National highways comprise 2.7% of India's total road network, but carry about 40% of road traffic.
5.National highways form economic backbone  of the country and have often facilitated development along their routes.