National Highway 31 is an important National Highway in India. It provides a gateway to the states of North-East India. The highway is long. It starts in Barhi, Jharkhand at the NH 2 and generally trends to the northeast, passing through Jhumri Tilaiya, Koderma, Nawada, Bihar Sharif, Harnaut, Bakhtiarpur, Mokameh, Begusarai, Purnea,  Dalkhola, Kishanganj, Bagdogra, Siliguri, Malbazar, Mainaguri, Dhupguri, Cooch Behar, Tufanganj, Kokrajhar, and Nalbari before ending at Jalukbari, Guwahati.