Perhaps it did. It is a useful insight, that may provide one of the answers.
What level of QA was specified for the manufacture of these structures? There is more than one way to track an item. There are differing levels of QA based on assessed risk and customer specification/contract. Was manufacture a batch process intended for multiple replicated items considered low risk, or a process suited to the supply of one off high risk items?
One possibility is that rather than a failure within the QA systems, it was a failure to implement an adequate level of QA.
The rub why products do not have end-to-end sign-offs is cost. A real world example is fuel line tube for a single engine prop airplane. It is exactly the same product as could be purchased in any auto parts shop for (my experience was long ago in a place far away - amounts for illustration as I do not remember the actual $ but make a point) $5/m; the airplane part was $45/m. The only difference was the airplane part had a part and batch number written on it in Sharpie pen so it could be traced back to the beginning of its manufacture. Install a part without that Sharpie written number and by definition the airplane was no longer airworthy.
In construction it seems key parts should warrant similar step-wise sign-offs for responsibility, not just process. Who approved diluting the cement mix, not just who approved how it looked when it dried?
This suggests the investigation has been thorough and the findings acted on.
Whether the actual investigation report has been released publicly is not immediately apparent.
In the interim, we are none the wiser as to how or why the failures in QC occurred, or as to the systems in place at the time. The ‘Primary cause’ has been attributed. The ‘root cause’ remains unstated.
That answer has not been provided.
Speculatively if the system of QA was not up to the task, would that go all the way back to the customer - Transurban or even Vic Roads?
In broader terms when planes crash, even those some like to attribute to pilot error, the investigations look for how and why the errors occurred to find solutions. Very few pilots deliberately set out to cause a crash.
Whether individuals involved with the QC are accountable or there is a broader concern, both require consideration.
