Diverging Diamond Intersection

The Diverging Diamond Intersection (DDI) allows free left turns for motorists. This is accomplished by shifting traffic to the left side of the roadway prior to it entering the intersection. Two-phase traffic signals are installed at the crossovers. Once on the left side of the arterial roadway, vehicles can turn left onto the frontage roads without stopping and without conflicting with through traffic. Through traffic on the frontage road bypasses the intersection via a Collector-Distributor (C-D) road under a bridge. Benefits include improved:​

• Safety
• Mobility
• Connectivity
• Frontage road traffic flow

A DDI is currently under construction in Williamson County to replace a traditional intersection at I-35 and RM 1431. DDIs are being considered for I-35 at Parmer Lane and I-35 at Airport Blvd.

​ Watch the DDI visualization to see how it works. ​​