We Bostonians are experts on tunnel crappiness. The horrible collapse in Minnesota got us wondering about the safety of bridges across our proud, crumbly nation.

According to the U.S. Department of Transportation 2006 report to Congress, Status of the Nation’s Highways, Bridges, and Transit: Conditions and Performance:

In 2006, 1,135, or 8.67%, of Minnesota's total inventory of 13,008 bridges were categorized as Structurally Deficient [SD]*.

For comparison:
In Massachusetts: 5,059 bridges were inventoried; 586 were SD. (11.51%).
In New York: 17,335 bridges were inventoried; 2,110 were SD. (12.16%)

And, some facts to ponder on your way to beg your doctor for some pre-road trip Xanax:
- In urban areas, 72.6 percent of the daily traffic is carried by bridges.
- Half of all bridges in the country were built before 1964.
- Bridges in the national inventory are, on average, 40 years old, with an average year of construction of 1964.
- Urban structures are slightly younger than rural structures, with an average year of construction of 1968.
- Bridges carrying Interstate routes are predominantly constructed of reinforced concrete, steel, and prestressed concrete.
- Concrete and steel superstructure bridges on the Interstate are, on average, 35 to 40 years old.
- Prestressed designs were introduced more recently and have become the predominant superstructure material employed today, with over 50 percent of new structures employing prestressed concrete.
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* It is important to note that, according to the report, "Structurally Deficient (SD)" does NOT mean "doomed." It just means "pretty lame."