On augus 1st 2007, as commuters were driving home from work on the 1-35W Mississippi River Bridge near Minneapolis, it abruptly collapsed. Thirteen people died and over a hundred were injured. The bridge had opened in 1967 and had not been scheduled for replacement until 2020. What had gone wrong? In 2008 the National Transport Safety Board concluded that extra concrete, which had been added to the bridge over the years as the level of traffic increased, had helped cause the collapse. After an inspection in 2005 engineers had classified the bridge as "structurally deficient", and repairs were planned. But many othei bridges in the area were thought to be in an even worse condition, so the work was not prioritised, and the true state of the bridge became apparent only when it failed, with tragic results.
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