Fri August 31, 2012  Time To Overhaul America's Aging Bridges?
This is SCIENCE FRIDAY; I'm Ira Flatow. Five years ago this
month, the I-35W bridge in Minneapolis collapsed, sending a full
load of rush-hour traffic into the Mississippi River. The
disaster injured nearly 150 people, killed 13. The bridge was
literally falling apart.  A year before the collapse, state
inspectors found that some of the bridge's bolts were either
loose, or corroded or missing altogether. In the words of one of
my next guests: Engineers don't specify unneeded bolts. But how
can we be sure something like that won't happen again? We
probably can't, because experts say that nearly 8,000 bridges
around the country are unsafe and in dire need of repair,
similar in some way to the conditions on the I-35W bridge before
it crumbled.  That doesn't mean they'll all collapse tomorrow,
of course, but there's a great deal of uncertainty about their
safety. You might be driving on one of them right now. And you
can find out if one of those ag