Bridges! We kind of expect them to just be there and do their job, ad infinitum. They are built into the landscape, and we often take them and the routes they open up for granted.

The reality, as any civil engineer will tell you, is that bridges are living, breathing things that require endless maintenance and monitoring to keep them safe, standing, and functional. A great example of this is found in the US Department of Transportation, and its publicly accessible register of bridge health reports.

Stay Standing

The thing about bridges is that we rely on them. They serve as vital transport links in our communities, ferrying people to and from work and school, and acting as the very arteries of commerce as trucks and trains haul goods to and fro. When a bridge crossing has to close, either for maintenance or at end of life, this link is severed, often with serious economic and logistical impacts. For that reason, we tend to like to keep our bridges in service as long as possible. The result, of course, is that if pursuing this goal means that proper maintenance and repairs aren’t seen to, there is a risk of collapse—which often comes with worse consequences. Loss of life is common when bridges fail, and replacing a collapsed bridge is often much harder and more time consuming than handling things properly ahead of time.

In the United States, it’s a well known fact that the bridges are getting old. The average bridge is 44 years old, which is bumping up against the 50-year service limit many were originally built for. Being an average number, it’s indicative that many bridges are exceeding that figure significantly. Obviously, a bridge’s age isn’t a perfect proxy for its condition, but closer examinations indicate there’s definitely a problem. A 2024 report from the American Road & Transportation Builders Association noted that 36 percent of US bridges are in need of repair or replacement, a total of 221,800 spans. 42,067 spans were considered to be in “poor” condition, which in their total see 168.5 million motorists crossing them every day. It’s a particularly sobering figure as it highlights the size of the disaster possible if these structures are to fail.

You can drill down into the data yourself if you desire. Within the Department of Transport, the Federal Highway Administration maintains LTBP InfoBridge, a database of information on bridges all across the country. It was developed by the Long Term Bridge Performance program, because the goal of the project is to understand how these structures hold up and perform over the decades. The database is publicly accessible, and serves as a portal for all the available data and statistics on how US bridges are doing. It hopes to enable everyone from state and federal authorities, to university students, faculty, and other researchers, to dive into bridge data and visualize and understand it better.

Data available is from a wide number of sources, including the National Bridge Inventory and National Bridge Element datasets, as well as climatic data collected from NASA’s MERRA-2 database. There’s also construction and design data sourced by the LTBP program, along with non-destructive evaluations that have been carried out. Data from various other special projects is available too, such as from Federal Highway Administration projects investigating timber bridges, steel weathering, and the use of ultra-high performance concrete structures.

If you have a particular bridge of interest, it’s easy to get a quick break down of how it’s doing. For example, you might like to know about the Vincent Thomas Bridge, in Los Angeles, California: National Bridge Inventory number 53 1471. It links San Pedro with Terminal Island, and is a suspension bridge with a total length of 6,060 feet and a longest span of 1,500 feet. Built in 1963, we can see from the data alone that it’s now showing its age.

The bridge condition is listed as “Poor,” and if we dive deeper into the National Bridge Elements data, we can see why. The health indexes of the deck, substructure, and superstructure have all been trending down in recent years as the bridge’s age has increased, with a particular drop off from 2019 or so. In particular, the steel cables and girders on the bridge have been showing their age, and the concrete columns supporting the bridge have been similarly degrading. The deck, too, is in need of repair, with the California Department of Transport recently dedicating some $706 million to replace it ahead of the 2028 Olympic Games.

InfoBridge also offers condition forecasts for many bridges across the country. For example, the 24th Street Bridge over Rio Linda Creek is currently listed as being in “Good” condition. Current forecasts show that the deck and superstructure is expected to be in much poorer shape somewhere between 2035 and 2055, while the substructure is expected to hang on in good shape for a bit longer.

You might think that you’d have to query a government department and delve deep into some dusty records room to learn about the condition of your local bridges. Instead, thanks to the efforts of diligent civil servants, you can instead access all the rich inspection data you like from the comfort of your own web browser. It’s not just good for citizen oversight, either. It aids local authorities and bridge owners in making the right decisions, by putting the necessary data right at their fingertips.

It also creates a certain level of accountability—having the data available means there’s little room for anyone to make excuses that they were unaware of a bridge’s condition prior to something going wrong. Ultimately, it’s just one arm of a project that hopes to take US bridges safely long into the future.

Featured image: “Brooklyn Bridge – New York City” by [Simone Roda]