The road system in Australia is very good, but as you leave the cities and head into the outback, road quality can vary greatly. Many rural roads are just dirt tracks and many washout during the wet season. Other roads turn into one lane for long distances requiring you to take your left wheels off the road to pass an oncoming vehicle.
Always carry along lots of water, sunscreen, hat, a good local map and a mobile phone if you’re driving out into the bush. Make sure you have a good spare tire, as some cheap Aussie tires don’t last long, especially on the hot roads at high speeds. It’s possible to breakdown hundreds of kilometers from the nearest town.