There are more than 24,000 bridges and structures in Iowa. The Iowa DOT is responsible for 4,092 that are part of the state’s Primary Highway
System, which includes the interstate, U.S. and "Iowa" state highways.
To provide access to information about Iowa's Primary Highway System bridges, the Iowa DOT has developed a Web-based application that allows
visitors to pinpoint a bridge in their area using Google Earth™ software and retrieve data about that bridge from the Iowa DOT's bridge
inventory database. Information available includes the year the bridge was built, year the bridge was reconstructed (if it has undergone
major work), average annual daily traffic count (AADT), highway it carries, feature crossed (waterway, highway, railroad, drainage ditch,
etc.), sufficiency rating, and whether the bridge is classified as structurally deficient and/or functionally obsolete.
The phrases "structurally deficient," "functionally obsolete" and "sufficiency rating" are federal terms used to identify bridges eligible for
funding assistance under the federal Highway Bridge Replacement and Rehabilitation Program. Structurally deficient refers to bridges needing
significant maintenance attention, rehabilitation or replacement. Functionally obsolete refers to bridges with deck geometry (e.g., lane
width, shoulder widths), load carrying capacity, vertical clearance or approach roadway alignment that no longer meet the criteria for the
system of which the bridge is a part.
The sufficiency rating formula is a method of evaluating factors that indicate a bridge's sufficiency to remain in service. The result of the
formula is a percentage in which 100 percent represents and entirely sufficient bridge and zero percent an entirely insufficient or deficient
bridge. Many factors are included in the ratings. The sufficiency rating doesn't necessarily indicate a bridge's ability to carry traffic
loads. It helps determine which bridges may need repair or replacement. Any bridge in Iowa found to be unsafe is removed from service until it
can be returned to a safe state of operation or replaced.
View a list of Iowa's primary highway bridges.
If you don't already have Google Earth,
download it for free
(14.3 Mb) and install it.
Click on Primary Structures (kmz 228 KB). Choose save to save the file to
your computer's hard drive. Once the file has been saved to your computer, a dialog box will appear. Then click open.
On the left hand side of the screen you will see a menu called Places. This shows a list of all bridges on Iowa's primary highway
system. Click once on the county to see information about the bridge, click twice on the county to zoom into the location of the bridge.
The bridge locations indicated as a green dot within the map can also be clicked to see the information.
U.S. bridge information addresses frequently asked questions regarding bridges in the federally financed U.S. transportation system,
including numbers of bridges, condition of the bridge inventory and work done in recent years to improve and invest in that inventory.