BridgesHere’s how to fix America’s crumbling bridges

By Henry Petroski

Published 26 November 2014

There are about 600,000 bridges in the United States, and about one in four is classified as functionally obsolete or structurally deficient. This doesn’t mean they’re in danger of imminent collapse; they may be simply too narrow or built for lighter traffic than today’s standards. Bridges that can’t support heavy trucks have weight restrictions posted. There are plenty of repairs that need to be done. With government funding for infrastructure projects being so tight, an alternative has arisen in what are called public-private partnerships, often abbreviated PPP or P3. In this arrangement, private investors assume the responsibility for financing and building a bridge or highway, and the investors are granted the right to collect tolls for what may be decades. The investors naturally believe they will realize a good return on their investment, even after they pay the public partner a sizable sum upfront for the concession. This upfront payment can be in the billions of dollars, which can be very tempting for a state or municipality struggling to balance its budget.

Professor Henry Petroski on the Duke University campus // Source: duke.edu

There are about 600,000 bridges in the United States, and about one in four is classified as functionally obsolete or structurally deficient. This doesn’t mean they’re in danger of imminent collapse; they may be simply too narrow or built for lighter traffic than today’s standards. Bridges that can’t support heavy trucks have weight restrictions posted. There are plenty of repairs that need to be done. But drivers groan when individual bridges are finally slated for reconstruction since these repair projects — along with accompanying traffic snarls — can seem interminable.

Who writes the checks?
The federal government pays much of the costs to repair and replace highway bridges, but it is up to the individual states to prioritize the work. Under current practice, the federal money comes principally from taxes on fuel — 18.4 cents per gallon on gasoline and 24.4 cents per gallon on diesel. The revenue goes into the Highway Trust Fund. However, because motor vehicles have become more fuel efficient and people tend to be driving less, the trust fund has been woefully underfunded in recent years. Last summer, Congress passed a stopgap measure to supplement the trust fund through May 2015. In the upcoming Congress, there’s likely to be considerable discussion about a more permanent fix.

The slow process of building a bridge
The traditional way a bridge has been built in America is for a state department of transportation to design the structure — either totally in-house or with the help of a consulting firm — and then issue a request for proposals from qualified construction companies. If not required to accept the lowest bid, the state may take into account such non-fiscal factors as past performance of the bidder, time to completion of the project and aesthetics. Only after a contract has been signed can construction begin.

This serial process takes time and delays can occur for a variety of reasons. Complications or contradictions in the design may arise, which can halt construction and require a return to the drawing board. When changes are necessary, disagreements can arise over who — the state or the contractor — should be held financially responsible. This can lead to legal challenges. Sometimes a contractor goes bankrupt in the middle of a job. Even when there are no technical or fiscal complications, environmentalists and other interest groups may call for a halt to work, which can also lead to further