Diverging Diamond Interchange (DDI)

A Diverging Diamond Interchange (DDI), also known as a double crossover diamond (DCD), is a diamond interchange that crosses traffic to the opposite side of the road across an interchange so vehicles have unimpeded movement onto the freeway ramps. Left-turn movements, which are a typical challenge with standard four-way interchanges, are eliminated with a DDI.

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In Operation DDIs 

In Operation

7
Under Construction 

Under Construction

4
In Development 

In Development

3

*On-system DDIs are on state routes.

 

 

 

A Diverging Diamond Interchange is an alternative interchange that crosses traffic to the other side of the road across an interchange. Left turns on and off the freeway ramps can now occur without crossing opposing traffic.

The DDI is best suited for intersections with heavy left turning volume on to and off the ramp, or locations that need additional capacity with limited right-of-way.

The exhibits below demonstrate the key characteristics and operations of a DDI.

DDI Operations

Exhibit 1-1. Key characteristics of a DDI., NCHRP Research Report 959, Diverging Diamond Interchange Informational Guide, Second Edition



DDI Key Characteristics

Exhibit 5-4. Key operational characteristics of a DDI., NCHRP Research Report 959, Diverging Diamond Interchange Informational Guide, Second Edition


  • Fewer conflict points.
  • Reduces wrong way entries to ramps.
  • Reduces speeds through the intersections.
  • Minimizes driver confusion.
  • Cost-effective interchange solution.
Legend Conventional Intersection Conflict Points DDI Conflict Points
Diverging 8 6
Merging 8 6
Crossing 10 2
TOTAL 26 14

Why DDI?

The innovative DDI design reduced potential points of intersection traffic conflicts and improves traffic flow and safety.

 

Safety Benefits

  • Fewer conflict points
  • Wrong Way entry to ramps extremely difficult
  • Reduced speeds through intersections
  • Minimal driver confusion


 

In Operation
ProjectLocationResources
I-285 at Ashford Dunwoody Road
DeKalb County
I‐85 at Pleasant Hill Road
Gwinnett CountyVIEW WEBPAGE
I‐85 at SR 140/Jimmy Carter Blvd
Gwinnett CountyVIEW WEBPAGE
I‐75 at Wade Green Road
Cobb County
I‐95 at SR 21
Chatham County
I‐75 at Windy Hill Road
Cobb County