Missouri’s Bridges: Are They Falling Apart?

As we’ve written many times before, the Missouri Department of Transportation (MoDOT) is facing a serious funding problem. If something is not done soon, MoDOT will no longer have enough funds to keep the state’s highways and bridges in a state of good repair. The emphasis for this post is on bridges, a subject that MoDOT officials often lead with when they promote measures that would increase the department’s revenue.

A likely reason for MoDOT’s focus is the fact that the condition of state-controlled bridges ranks poorly compared to other states. Congestion may be low and road pavement tends to be smooth, but Missouri is among the bottom tier of states when it comes to the number of bad bridges. MoDOT claims that 2,000 bridges in the state are “structurally deficient and functionally obsolete.” Bridge closures, like the recent emergency shutdown of MO 291 in Kansas City, also receive significant media attention.

However, the claims that Missouri’s bridges are in crisis is somewhat misleading. Missouri has an extensive state highway system that includes not only the high-profile bridges across major rivers, but also many lightly used bridges that cross small streams. In other states, the latter usually belongs to counties or municipalities instead of the state transportation department. In Missouri, these numerous small bridges greatly add to the list of structures in need of repair.

To illustrate this fact, let’s consider MoDOT-controlled bridges in a condition listed as poor or worse in the National Bridge Inventory, of which there are 735. As the chart below demonstrates, the majority of these bridges are lightly traversed (less than 1,000 vehicles per day). In fact, less than 4 percent of bridges in poor or worse condition have daily traffic that exceeds 40,000 vehicles a day.

Caption: 1. Frequency refers to the total number of bridges in a range of daily traffic, like the total number between 0-1,000 vehicles per day.
2. Cumulative % refers to the percentage of poor quality bridges that have traffic levels at or below the designated range.

Looking at the location of bridges, we can see that the vast majority of structures in poor condition are located in rural areas away from major highways, which in other states would be the responsibility of county or local governments:

This demonstrates that the low-traffic bridges are in the worst shape; they are in most danger of closure if the “325 Plan” goes into effect. It is unlikely that a major, well-trafficked highway will have to shut down after a piece of the bridge crushes a school bus, as some alarmists have envisioned.

When we take away the many small bridges that do not see much traffic, Missouri is left in the same position most states are in: a few dozen ailing bridges that need attention. As for those small local bridges, it might be best if over time MoDOT returns those routes to the control of local governments, who can better perform a cost/benefit analysis on reconstruction proposals.