If I had to place blame here I would blame the INDOT maintenance crew for not keeping the bridge maintained so that things like this could have been prevented.
The facts will come out, but that judgement is currently premature. If there is blame - keep in mind the bridge has reached its design life, it could lie with:
- INDOT inspectors if they didn't follow procedures (if they even inspected this bridge)
- the contractors hired by INDOT if they didn't follow procedures (if contractors did the inspections which is what was said)
- FHWA bridge inspection procedures or requirements could have been lacking
It could be any of the four, a combination, or something else completely. Eventually, any bridge or structure will deteriorate so it could simply be a symptom of age.
If anyone has facts, they can assess blame. Otherwise, it is guesswork at best.
On the size of the crack, didn't they say it has been there since 1962, and they don't know if it grew over time? I personally have no idea, but it will be interesting to hear what the results of further testing will be.