"Melburnians supposed psychological attachment to their cars long been used as a reason for not upgrading public transport, but I wonder if it's really true. Whilst people aren't always rational (some might say aren't often rational), they do still respond to incentives, and if the train gets them to work faster/more comfortably than their car then my feeling is that they would take the train. Whilst I don't have the datasets (or the patience) to undertake comprehensive statistical hypothesis testing, there's plenty of map based data from the ABS and DPCD which should offer some good insights into the question.
Some basic assumptions
The idea that Melburnians are wedded to their cars implies that public transport use is not a function of public transport quality - if it were then it would be a good indication that people were making transport decisions based on the merits of their options. To test this, we can compare public transport modal share and average cars per household in parts of the city with good and bad public transport quality. To assess what constitutes a good public transport service, I'm going to take a very simple approach - namely that trams and trains are good, and that buses are bad. It's certainly a simplistic assumption, but a largely necessary one if I'm to use the map data. In any case, I think it's fair to say that, on average, the quality of service on Melbourne trains and trams is much higher than on buses.