Laura Bliss is CityLab’s West Coast bureau chief. She also writes MapLab, a biweekly newsletter about maps (subscribe here). Her work has appeared in The New York Times, The Atlantic, Sierra, GOOD, Los Angeles, and elsewhere, including in the book The Future of Transportation.
Explore the daily traffic count and structural status of 600,000 bridgespans.
About 10 percent of America’s 600,000 bridges are structurally deficient, requiring “significant maintenance, rehabilitation or replacement,” according to a 2013 report by Transportation for America. Many of them have exceeded their intended lifespan by more than a decade, and yet Americans continue to use them, taking 260 million trips over deficient bridges on a daily basis. Alarming stuff, especially now that the cartographer and GIS consultant Jonah Adkins offers us a new opportunity to stare down this data on a map.
In the new dot map Bridges of America, Adkins lays out the sorry facts of the Federal Highway Administration’s National Bridge Inventory, which accounts for data on bridge type, structural conditions, average daily traffic, and more, going back to 1992. You can zoom and explore the country’s bridgespans and viaducts by their daily traffic count or by their condition: “Ok,” “Structurally Deficient,” or “Functionally Obsolete.” (There are other types of labels that the FHA gives to bridges, but Adkins says he settled on the three that were easiest to understand.)
Counterintuitively, that “functionally obsolete” label isn’t actually as bad as “structurally deficient.” The first term usually means the bridge doesn’t meet current design standards, but could still be in decent shape. So that’s a bit of a caveat to reading Adkins’ map, since the red color gradient he uses seems to suggest that “obsolete” is the worst type of bridge America is dealing with. (If only.)
Now, not all “structurally deficient” bridges pose an immediate threat to the safety of those who cross them, either. But the longer they go unattended, the higher the costs of repairing them will be. With gas tax revenues in perilous decline, the old financing options for fixing these bridges are out. Legislators would do well to look to places like Oregon, with its new per-mile gas tax program, for new ways to support our poor old bridges.