Couple from Agity
This needs further investigation, and there is a very good chance that one of Balko's suggestions for how it happened is right, but they aren't exhaustive. Shit happens, and not everything can be controlled. Should they have inspected the overpass every two months? Every month? Every week? Should they have spent twice as much time on each inspection? Four times? Etc. There are only so many resources to go around. Perhaps more need to be put to use in this area, or the resources currently used could be better used doing the same things (working harder for instance), but at this point it doesn't look clear to me what the problem is.