Crumbling Bridge, Flaming Mazda.

King Banaian has a post that reflects an economist's view of the Bridge in the River:

Begin with the observation that no bridge can ever be perfectly safe. Rational allocation of scarce resources must involve marginal analysis: We allocate the money to make transportation safe up to the point where the marginal benefit of investing the dollar in project A is equal to that of project B is equal to that of project C, etc. And we invest only an amount where the increase of safety is worth the expense of providing it.

This is much closer to the view legislators must adopt in the real world — versus the rhetoric of candidates and politicians who aren't actually charged with solving the problem.

I heard  a similar and more accessible description of the analysis on MPR. A Colorado highway official was being interviewed about the state's bridges, and the reporter suggested an apt analogy between "structurally deficient" bridges and used cars.

We all make judgments about how long to keep pouring money into our cars. If you're like me, you take good care of your car but drive it for as long as you can. At some point, it clearly becomes structurally deficient —  burning some oil, quarter panels rusty, on its third set of rotors, muffler corroded, maybe a crack in the windshield. But it's driveable, safe and still far less costly to operate than a new car with a monthly payment.

I once drove a rotary engine Mazda until it caught fire for the third time. It was a snowy winter, after all, and the blazes on the engine block could be quickly extinguished, with no apparent effect on other functions of the car.

I'm no economist or bridge inspector, but after the third fire, I could see it was getting to be time for replacement.

We should not blame MN/DOT for its analysis, assuming no grievous misjudgments were made about bridge condition. But we should revisit the question of where we want to be as state on scale of new car to flaming Mazda.

How many of us would rather not have to bolt for the snow drifts on our way to work in the morning?

Comments

[spotty]

Charlie, Think about how much sooner society would have expected you to replace that car if the risk was not simply that you would be left stranded somewhere, but that the car might explode and level a city-block wide area. The example you pose is private decision-making without consideration of the potential externalities. Public decision making, which is about the public good, is mostly about consequences to the public at large.

[Charlie Quimby]

I think we are making the same point.

I'm not at all posing my personal example as the correct model for public decision-making; it's to highlight the shortcomings of assessing and managing the public good according to a too narrow set of considerations — especially personal.

But I don't quite buy your reading of my metaphor. If believed my car posed the explosion risk, I'd have replaced it sooner, too, my personal interest in staying alive clearly aligned with the public good of not blowing up my neighborhood. That's the Carol Molnau "my daughter drives on that bridge" argument.

I think the Flaming Mazda example fits better if you think about everyone carpooling with me, not just watching the car go down the street. As a whole, the public would not accept my view that the car was safe and economical to drive — even if I could present a marginal analysis in support of my decision, showing carpoolers that their contribution to the kitty was smaller.

In fact, my carpoolers would bring a wide variety of concerns, personal risk tolerance and spending thresholds. We'd have to work something out that was going to cost more than the snowball solution. It would be wrong for me to veto their concerns because I'm the driver and have an aversion to spending.

But the concerns were vetoed.

In Minnesota, a certain amount of crumbling public infrastructure (it's considered safe, remember) was tolerated by the people in charge. They made a political as well as economic calculation that we'd rather have a few more pennies in our pockets to help make our new car payment.

But when a bridge goes down, Escalades and Fiestas fall at the same rate of speed.