"When do you think we'll have the next major bridge collapse?" Polly Trottenberg, assistant secretary for transportation policy for the U.S. Department of Transportation, had just given a very interesting and entertaining talk at a Transportation Research Forum lunch and was graciously taking questions. My question seemed reasonable to me, but she was obviously taken aback a bit by it. Her response was, "That's a morbid question." Perhaps it is, but it's one she and her colleagues should be thinking about.

Steel rusts and concrete deteriorates. The laws of physics are inexorable and do not respond to our wishes or our votes. On Aug. 1, 2007, the Interstate-35W Bridge over the Mississippi River at Minneapolis collapsed, killing 13 people and injuring 145. In his book "Too Big to Fall," Barry LePatner writes, "There are 7,980 structurally deficient and fracture critical bridges, many of them weakened and moved closer to failure by years of inadequate maintenance. No engineer would take issue with the fact that many of these bridges are as close to collapse as the I-35W Bridge was in the years leading up to its failure."

Maybe it's my many years as an auditor that make me think "morbid" thoughts, but thinking about risk—probabilities and costs—is a critical part of developing sound public policy, especially when the costs are human lives. Considering the facts that LePatner reports, it seems pretty clear that the probability of a major bridge collapse is about 100 percent. So here is a policy issue where the risk level is essentially off the charts—extremely high costs and extremely high probability.

You know the drill. When the next big bridge collapses, there will be shock and outrage. Investigations will ensue. Who knew what and when did they know it? Who's responsible? What—in hindsight, of course—should have been done and who should have done it? And, of course, what political gain can be made from such a catastrophe? It may not happen before this November's election. Indeed, we may actually dodge the bullet and take the actions needed before it happens. But recognize that that is extremely hard to do. The choices—close a critical bridge or find huge sums of money to fix it—are both very difficult to do under the best of circumstances. And, given the current political and fiscal climate, these are not the best of circumstances.

But still, nothing may happen in 2012—we may do nothing and no bridge may fall. If so, it would be well to remember the words of a Nobel Prize-winning physicist quoted in LePatner's book. During the investigation subsequent to the 1986 explosion of the space shuttle Challenger, Richard Feynman said, "The fact that this danger did not lead to a catastrophe before is no guarantee that it will not the next time, unless it is completely understood. When playing Russian roulette, the fact that the first shot got off safely is little comfort for the next."