Highway 1 of Australia is with a length of 14,500 km (9,000 mi) the longest national highway in the world. It can be considered a giant "ring road" as it except for a few shortcuts in the north follows the entire coastline of mainland Australia.
Part of the road also traverses Tasmania. Highway 1 is the only route to reach across all Australian states.
Circumnavigating mainland Australia, this road goes through all states and their capitals and through or near most major attractions in Australia (two major omissions being Canberra and Uluru). Therefore, if you have time and don't mind long driving distances this is one of the best ways to see almost all of Australia.
Created in 1955 out of existing state and local roads and tracks, Highway 1 is actually a network of roads. It's marked "1", "M1", "A1" or "B1" depending on the type and the quality of the route.
Australia is a huge country and doing the whole Highway 1 will certainly take several weeks; even the shortest of the sections below are almost a 1,000-km drive.
Especially in the western two thirds of the country, expect there to be stretches of several hundred kilometres between roadhouses where you can get fuel, food and water.
During the Austral summer, it can get extremely hot in the daytime which isn't only dangerous for travellers but also puts stress on your car's cooling system and battery. Heat and drought are also often followed by major wildfires.
According to en.wikivoyage.org