I'm not a bridge engineer, but it seems that the rating analysis of bridges may be part of the problem. It doesn't seem that it really provides an analysis of the actual risk so that decision makers can factor that into the O&M decisions. A risk assessment procedure for rating bridges might be more useful. This is often done with dams and could easily be done for bridges also. By constructing a dam or a bridge, you are creating a potential hazard if it fails. O&M of dams often involves risk assessments which looks at the probability of failure and the consequences of that failure. This analysis of risk can guide dam owners and the public in the necessary maintenance, inspections and mitigation measures to take.
Using the risk assessment example, if risk had been evaluated for this bridge, more proactive O&M might have been considered necessary. Even using a qualitative assesment, the bridge would be considered high risk. Probability of failure due to fatigue cracking, age, lack of redundancy, ship collision, etc. would have certainly been higher than normal. And consequence of failure for this bridge are very high due to the high traffic volume, economic impacts, environmental impacts, loss of life and cost to replace. A risk assessment would have likely shown this bridge to be at the high end of the risk spectrum as compared to other bridges in the state. Perhaps a new model for evaluating bridges should be considered.