The first Diverging Diamond Interchange (DDI) in the United States opened in Missouri in 2009. There are now more than 200 interchanges of this type across the country. DDIs can reduce the number and severity of collisions compared to a traditional diamond, and reduce traffic congestion. Vehicles traveling through the DDI cross over to the opposite side of the roadway so that left turns no longer cross the path of oncoming traffic. While crossing to the opposite side of the road may sound confusing, vehicles are guided through the interchange via use of channelized islands and signing and striping enhancements on the roadway make the routes very clear for drivers to get accustomed to the new design. Removing left turns from the traffic signals greatly increases the number of vehicles that can pass through the signal during a cycle.
DDIs have been shown to improve safety as well as traffic flow. A conventional diamond interchange has 18 conflict points, or locations where collisions can occur. A DDI reduces this to 8.