In the Northern Territory, Highway 1 is a 1,414-kilometre (879 mi) long route with a 316-kilometre (196 mi) long spur, that connects Darwin to northern Western Australia and Queensland. The route traverses the territory, from the Western Australian border near Kununurra, to Katherine, and then across to the Queensland border near Wollogorang, with a spur section linking Katherine to Darwin. Highway 1 continues around the rest of Australia, joining all mainland state capitals, and connecting major centres in Tasmania. All roads within the Highway 1 system are allocated a road route numbered 1, M1, A1, or B1, depending on the state route numbering system. In the Northern Territory, the highway is designated as National Highway 1 where it is concurrent with the National Highway routes linking Darwin to Adelaide and Perth. The eastern section from Daly Waters to Queensland is designated as National Route 1.

In New South Wales, Highway 1 is a 1,351-kilometre (839 mi) long route that crosses the state, from the Queensland/New South Wales border near Tweed Heads to the Victorian border near Timbillica. It provides the main coastal route between Brisbane and Melbourne via Sydney. Highway 1 continues around the rest of Australia, joining all mainland state capitals, and connecting major centres in Tasmania.