Q: S1: National highways connect one state with another and are of national importance. S6: These road systems are also known as primary road systems and are laid and operated under the supervision of the National Highway Authority of India. P: They are important because whereas they constitute merely two per cent of the total road networks, they nevertheless carry 40 per cent of the total road traffic. Q: The road infrastructure of the country is therefore crucial, and their construction and maintenance is of critical importance. R: They bear the load of traffic because these roads connect long distances and pass through major cities and towns. S: Since they cover the length and breadth of the nation and connect cities and towns, these highways are the primary facilitators of trade and connectivity.