Bridge design is something most people do not think about until there is a major accident, such as the collapse of the Minneapolis Interstate 35W bridge on Aug. 1, 2007.

Nor is the average person much concerned with safety reviews of bridges until such a tragedy occurs. The bridge that folded and plunged into the Mississippi River took 13 lives and injured 145 people.

Engineers who designed the span in the 1960s made a mistake on the steel gusset plates that hold the bridge together. The plates needed to be thicker and stronger, according to the National Transportation Safety Board.

One lesson taken from the incident is that state transportation officials may not look closely enough at design factors when they inspect bridges. The Minnesota span stood for 40 years, but the weight of construction equipment coupled with rush-hour traffic proved too much for the structure on the tragic day.

Safety investigators have done a wide review of bridge design and review procedures in several states. Ten of 14 states told the safety board that they had discovered at least one design flaw in their bridges.

Ten flaws among 80,000 bridges is not a disturbingly high occurrence — unless you or someone you know is victimized by such a mistake.

Federal officials are thinking about proposing national design review standards. That alone indicates a concern. One safety board member called the bridge collapse "a wake-up call" for the government and bridge designers.

In all these efforts, safety must be the top priority.