The Northern Territory is the most sparsely populated state or territory in Australia. Despite its sparse population, it has a network of sealed roads which connect Darwin and Alice Springs, the major population centres, the neighbouring states, and some other centres such as Uluru (Ayers Rock), Kakadu and Litchfield National Parks. Some of the sealed roads are single lane bitumen. Many unsealed (dirt) roads connect the remoter settlements.[1] Major roads are classified into three categories: National Highway, Arterial Roads, and Secondary Roads.[2]