Diverging Diamond Interchange (DDI)

These interchanges have been shown to increase capacity and safety, decrease congestion and minimize the cost of new infrastructure.

Benefits & Advantages:

  • Safety – Reduces the number of ways vehicles can collide by almost half (14 compared to 26 for a conventional diamond interchange).
  • Greater capacity and efficiency – Accommodates more traffic than conventional designs. Drivers make free-flow right and left turns on to the major freeway.
  • Easy navigation – Guides drivers with overhead signs, pavement marking, and traffic signals.
  • Meets the needs of all road users – Accommodates large trucks, pedestrians and bicyclists.

Navigating A DDI:

  • Drivers follow the signs, signals and pavement markings to cross through the intersection at the first set of traffic lights. Traffic appears as if on a one-way street.
  • All left turns onto the freeway are free flow, meaning vehicles do not have to stop to access the ramp.
  • Vehicles going straight simply proceed through a second set of traffic lights.
  • Pedestrians travel on designated walkways and cross only at the crosswalks.
  • Bicyclists may choose to use the bike lane or pedestrian walkways and crosswalks.


  • For improvement projects, a Diverging Diamond interchange often uses the existing bridge structure and the existing right of way, which eliminates the cost of building new structures and purchasing additional right of way. 
  • Because many of the existing interchange features remain intact, the Diverging Diamond interchange is often built in less time than it would take to build a new interchange and with significantly less impact to motorists. 
  • A Diverging Diamond interchange usually requires the purchase of less right of way and the construction of fewer lanes and bridge structures than traditional interchange types.



Dakota News Now: What will the DDI look like when complete?

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