I also live in Minneapolis. Minneapolis actually does have fairly bad traffic, mostly due to poor road system design (several "commons" areas, several major left exists) and lack of capacity.
That bridge was "bumper to bumper" only in one direction for each rush hour. Also, the construction had a couple of lanes closed in the busy direction, so there were fewer cars on it than normal. Only 2 lanes in a single direction were "bumper to bumper" at the time. 6pm is also after the "height of rush hour" in Minneapolis, though not by much.
There are lots of bridges that don't have piers in the water. There are also truss bridges that do have piers in the water (see Wichert truss for an example). The Minneapolis bridge did have a rather long span, but my no means extraordinary. The longest steel-truss bridge that I'm aware of has a span of over 1500 ft, while the Minneapolis bridge span was under 500 ft.
I can't wait to read the NTSB report on this one. My guess is we'll hear about dated inspection techniques that failed to find fatigue fractures combined with an economic incentive to keep existing bridges for as long as possible.
Quite some time ago, I heard a book excerpt from
"The Edge of Disaster" on NPR about the nation's aging infrastructure. A few months later, NPR's Talk of the Nation had an hour dedicated to
"A Critical Look a the Nation's Infrastructure". Naturally, nobody cared until there was another collapse, and now there is an emotional, un-thought-out outcry to DO SOMETHING! Sort of reminds me of the airport security stupidity after 9/11.
Thanks to Bitt for teaching me how to recover this post...
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