Diverging Diamond Interchange

A diverging diamond interchange (DDI) is an intersection design that allows two directions of traffic on the crossroad to temporarily divide and cross to the opposite side to gain highway access more easily. The difference between a DDI and a conventional interchange is the design of directional crossovers on either side of the interchange. This eliminates the need for vehicles turning left to cross the path of approaching vehicles. Two-phase traffic signals are installed at the roadway crossover points. Once on the left side of the roadway, vehicles can freely turn left rather than waiting for oncoming traffic to clear or for a left-turn signal. Through-traffic on the frontage road is handled via an intersection bypass lane and proceeds straight through the cross-street intersection allowing vehicles to avoid the traffic signal. Benefits include improved:

  • Safety
  • Mobility
  • Connectivity
  • Frontage road traffic flow

A DDI is in operation at I-35 and RM 1431. Two other DDIs are under construction at I-35 and Williams Drive, and I-35 at Parmer Lane. One is also being considered for the intersection of I-35 at Airport Boulevard.

Watch the DDI explanatory video below to see how it works. You may also view or download the DDI fact sheet.

DDI Explanatory Video