From rural covered passes to modern engineering marvels, bridges overcome natural obstacles and expedite transportation. Yet many of the bridges that people drive on every day are in rough shape. According to one transportation group, more than one in 10 of the country's bridges are in need of serious repair or replacement.
In many states, the situation is more dire. Nearly a quarter of the bridges in Pennsylvania are structurally deficient, the highest of all states, according to Transportation for America, a grassroots organization advocating updated transportation infrastructure.
Based on the group's report, "The Fix We're In For: The State of Our Nation's Bridges 2013," these are the 10 states with the most dangerous bridges.
The states on this list tend to have older bridges — their bridges' average age is older than the average age of all bridges nationwide of 43 years. In Pennsylvania, the states with the most dangerous bridges, the average age is 54, higher than all but four others.