It's hard to really say just how badly corroded the bridge decking was. That was one of the reasons given for replacing it though. Having said that, bridges have a design life and 70 years was probably pushing it. I've heard that many of the bridges on the interstate system are past the life they were designed for too. Once in a while, warnings aren't heeded and a bridge collapses with tragic consequences, so there is something to be said for replacing before collapse.
Probably the worst part of our old bridge was it wasn't very farmer friendly. Too narrow and heights were limited too. Next closest bridge was 20 miles of winding gravel road to the east so that presented a considerable hardship for big loads.
I and most others are very glad for the new bridge. Just hope we don't get too many more spring & summers like 2011.