Driving in Australia
Australian road rules vary slightly from state to state, but mostly adhere to a consistent set of road signs, lane markings and driving laws. The main differences are the maximum speeds allowed, the speed tolerances above the posted limit, and the minimum driving age. For example you can drive at 16 in Victoria but must wait until 18 in New South Wales. If you have a licence from the UK and you are 17, you will need to wait until you are 18 until you are allowed to drive.
Signage tends to have the same icons as international standards but is often a different colour or shape, even to New Zealand. There is no free left turn on a red light except where signage permits.
Road markings vary slightly. Notable differences:
Australia operates a graduated driver licence (GDL) system consisting of a theory test (known as a Driver Knowledge Test) and a practical test followed by two periods of gathering experience as a provisional licence holder (P1 and P2) before being eligible for a full licence. You must carry your driver's licence with you at all times when driving.
Different states have different requirements for overseas drivers (check with the local traffic authority - links below). For example, in New South Wales you can only drive on a foreign licence for three months until you have to change it for a NSW licence, whereas in Victoria you can drive for 6 months.
Licences in a language other than English must be accompanied by an authorised translation into English.
Some countries' licences receive preferential treatment. New Zealand licence holders are usually eligible for an Australian driver's licence without taking a test. Other countries may have to take a theory test, and others may have to take both the theory and practical test.
The length of time you have held a licence in your native country, and the type of licence it is, determines what licence you will be eligible for in Australia.
 State licensing websites
 Speed Limits
Speed limits are posted in increments of 10 km/h from 10 to 130 km/h. The signs are a red circle with a white centre and black writing.
Demerit points are given if you are caught speeding. Demerit points are doubled on public holidays in some states. Some states have much less of a tolerance for being over the limit (Victoria being the strictest with approximately 3 km/h leeway).
Note that corner advisory limits are shown with black writing on yellow signs and will always end in 5, e.g. 35 km/h
Australia has one of the highest vehicle usage statistics in the world due to the long distances between major centres. Motorways are only present in the larger cities. Travelling between cities may include periods of single carriageway road, or long periods of straight roads across featureless plains (e.g. from Perth to Adelaide across the Nullarbor plain).
There are many roads which are unsealed.
Large animals can be a problem on the roads after dusk. Kangaroos and wallabies can jump out in front of your car. Wandering stock is a problem when you head towards the outback. Emus are large, solid birds that can cause a lot of damage, and cassowaries are large endangered birds that have little road sense, too.
 Intersections (junctions)
Intersection rules are consistent throughout Australia.
It is compulsory to stop at a STOP sign unless directed by a police officer. Instructions from a police officer override all signs and lights at an intersection.
You must give way to your right on uncontrolled crossroads.
On a T-intersection traffic travelling across the top of the T has right-of-way over traffic approaching the T from the bottom.
All intersection rules are explained here
Roundabout rules are consistent throughout Australia. The rule is to indicate your intended direction and 'signal off' the roundabout.
To turn right, approach the roundabout in the right-hand lane signalling right (your intended direction). Once you pass the exit before the one you want to take, signal left (signalling off) to exit the roundabout.
To pass straight through a roundabout, approach the roundabout in any lane that has an arrow pointing straight ahead, without signalling (your intended direction is straight, therefore no signal is required yet). Once you pass the exit before the one you want to take, signal left (signalling off) to exit the roundabout.
To turn left, approach the roundabout signalling left (your intended direction), and exit the roundabout at the first exit.