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"Show Me" State Shows America The Benefits of Diverging Diamond Interchanges

Posted by Acting Federal Highway Administrator Brandye L. Hendrickson

All of us at the Federal Highway Administration (FHWA) are proud to partner with state, local and tribal governments to encourage the use of state-of-the-art transportation innovations under FHWA’s “Every Day Counts” (EDC) initiative. We call EDC the “on-ramp to innovation,” and with good reason. We’re always looking for newer, better ways to keep Americans safe while they drive and save time in project delivery as well as taxpayers’ money.

Missouri – also known as the “Show Me State” – has spent the last decade becoming the nation’s leading champion of Diverging Diamond Interchanges (DDIs). Throughout my career, I have seen few safety improvements as effective as DDIs.

DDIs are great because they eliminate the need for expensive left- or double-left turn bays by allowing left-turning vehicles on the crossroad to make a free turn left directly onto the onramp. In short, they keep drivers safe by reducing the number of intersections or other places where collisions can occur.

MoDOT created the first DDI in 2009 on I-44 in Springfield, Mo. Within a year, it reduced injury-only crashes by 80 percent and all crashes by 53 percent. In the decade since, MoDOT has created 19 more DDIs. The latest addition to its “diamond” collection, at I-49 and 155th Street in Grandview, is an especially good example of better transportation because it uses a roundabout (another EDC innovation supported by FHWA) at one of the ramp terminals instead of a traffic signal. Mixing these two proven safety measures has led some to start calling the combination a “divergeabout.”

During this year’s Infrastructure Week, FHWA is underscoring the importance of innovation and the workers responsible for building and maintaining our transportation infrastructure. Kudos to workers in Missouri and across the country who are helping to build roads and bridges. Pleases how these hard-working men and women your thanks by driving safely when traveling through highway work zones.