As feral says, the two most populous states, Vic & NSW, differ in that NSW has these tests and Vic does not. The difference in accident rates over the years is pretty small, and almost always better in Victoria. This of course has nothing to do with the lack of annual tests, but has a lot to do with the better roads.
The fact is that not only are very few accidents due to vehicle defects, but the ones that are due to these defects are most commonly due to tyre defects, that can and do develop well within the inspection interval.
The annual tests in NSW, in my view, make no significant contribution to road safety but do keep a lot of mechanics in bread and butter (not only in doing the tests, but in fixing problkems uncovered).
John

