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What is a Diverging Diamond Interchange and How Might it Help Traffic in Round Rock?

North Carolina Department of Transportation

State transportation authorities announced this week that they received the green light to build a $6.7 million "diverging diamond interchange" at I-35 and University Blvd. in Round Rock. That's an area that gets a lot of traffic, partly because it's near the only IKEA in Central Texas and the Round Rock Premium Outlets, among many other retail businesses.

"We are very excited," Kelli Reina with the Texas Department of Transportation says. "We are starting the state's first diverging diamond interchange." Construction is set to begin this fall. 

Most Texans are probably unfamiliar with the diverging diamond interchange, a traffic innovation developed by Gilbert Chlewicki in 2000. But the U.S. Department of Transportation says it can allow for up to 650 left-hand turns an hour, double the normal amount. (The intersection design is also known as a "Double Crossover Diamond Interchange," just to add to the confusion.)

A diverging diamond interchange is supposed to make turning left safer and easier by moving traffic from the right-hand side of the road to the left for turns on to the interstate. The easiest way to understand is to see it in action. This video from North Carolina's Department of Transportation does a decent job explaining it. 

Nathan Bernier is the transportation reporter at KUT. He covers the big projects that are reshaping how we get around Austin, like the I-35 overhaul, the airport's rapid growth and the multibillion-dollar transit expansion Project Connect. He also focuses on the daily changes that affect how we walk, bike and drive around the city. Got a tip? Email him at Follow him on X @KUTnathan.