Iowa DOT bridge condition story map gives more accurate snapshot of Iowa's infastructure

H34B-MISC-1It seems like there has been a lot of gloom and doom in the media lately about the condition of our country’s roads and bridges. While it’s true that the need to improve our infrastructure in Iowa is outpacing the funds available to repair or replace every bridge quickly, having accurate data displaying in a way that’s easy to understand is critical to being able to accurately understand the condition of our infrastructure.

The Iowa Department of Transportation’s bridge condition story map helps explain how bridge condition in the state is trending. It’s an interactive way to present data that allows users to see layers of information on state, county, and city owned bridges.  Each layer indicates the total number of bridges in that area and a breakdown of the condition, serviceability (or usefulness based on current design standards), and weight restrictions in place. In addition, the map allows you to zoom in and get detailed information for any individual bridge in the state.

ALL_Bridge_DataScott Neubauer is the Iowa DOT’s state bridge maintenance and inspection engineer. He said, “Our inspectors inspect bridges year-round, so the data is being updated constantly. In the past we used an annual ‘snapshot’ of bridge conditions, but using an algorithm with the mapping technology, we can show in nearly real time the condition of each structure. We feel the algorithm we use is a better indicator of actual bridge conditions than others that might be out there.”

This bridge rating system is unlike any other in the country. Neubauer said, “We came up with our rating system to help identify and set priorities for which bridges to include in the five-year transportation improvement program. Creating this map helps us visually tell the ongoing story of our structures.”

Condition index definitionsNeubauer developed the algorithm for a bridge condition index from 0 to 100 that is used to determine Good, Fair, and Poor totals that feed the map. The algorithm includes structure condition, capacity, clearance, information on the waterway beneath the structure and the type of highway carried by the bridge.

He said, “When we calculated the bridge condition index for every bridge in the state, we found the natural delineation of a ‘Good’ rating would fall at 70 and up. To gain a ‘Fair’ rating, the bridge would score between 37.5 and 70 and anything at 37.5 and below would be rated as ‘Poor’.”

Bridge definitionsThere are some scary words commonly used when talking about the state of our bridges. Functionally obsolete and structurally deficient are terms the media often uses to talk about bridges in need of repair. While both terms are somewhat helpful, they don’t give an accurate picture of the condition of each bridge. It’s important to remember that none of these terms necessarily mean that a bridge is unsafe it only indicates that we have to look at that bridge differently than we would a bridge not listed in one of these conditions.

To find the Iowa DOT’s bridge condition map and other performance-related information, go to and click on the “performance” tab on the left side of the screen. 






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