The Telegraph recently featured an article about the availability of cheaper parking on the edges of the Sydney CBD. For people willing to take the hike, they claim it is cheaper to park there than catch the train daily to work from the outer suburbs (they conveniently forgot about fuel and maintenance of the car). Brisbane has similar options for people willing to get a little exercise.
This is great for increasing physical activity of commuters but it doesn't do much for reducing traffic into the city. Interestingly, people who choose to do this do not get captured in the census as there is no 'park and walk' option in the journey-to-work survey.
Another active commute option that is growing in popularity is 'park and cycle'. The improved cycle facilities serving the CBD, and the high cost of parking and public transport make driving and cycling a very attractive option. Where there is free parking that is close to good cycle facilities into the city you will notice the park and cycle commuters.