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Diverging Diamond Interchanges

 
 

A Diverging Diamond interchange allows two directions of traffic to temporarily cross to the left side of the road. It moves high volumes of traffic through an intersection without increasing the number of lanes and traffic signals. This movement provides easier access to an interstate. 

Driving Through a Diverging Diamond Interchange

When driving through a Diverging Diamond interchange, motorists proceed through a traffic signal at the entrance to the interchange and simply follow their lane to the opposite side of the roadway.

  • Motorists needing to access the interstate turn left on the on-ramp without having to stop for additional traffic signals or wait for oncoming traffic to pass.
  • Motorists needing to drive straight through the intersection proceed through a second traffic signal and follow their lane back to the right side of the road.

Pavement markings and signals direct motorists to where they need to go.

Pedestrians & Cyclists

Pedestrians use signalized pedestrian crossings and are then directed to a center pedestrian island in the middle of the road. Bicyclists can use a bike lane adjacent to the right lane or a median bike lane if one is provided.

Benefits of Diverging Diamond Interchanges

Safety & Efficiency

A Diverging Diamond interchange allows free-flowing turns when entering and exiting an interstate, eliminating the left turn against oncoming traffic and limiting the number of traffic signal phases. It is also easy to navigate, eliminates last-minute lane changes and provides better sight distance at turns, which results in fewer crashes.

The design also reduces congestion and better moves high volumes of traffic without the need to increase the number of lanes in an interchange.

Cost-Effectiveness

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.

Diverging Diamond Interchanges in Use

The United States’ first Diverging Diamond interchange opened to traffic in 2009 at the intersection of I-44 and MO 13 in Springfield, Missouri. The Missouri Department of Transportation built the interchange in about six months, while maintaining traffic at the location throughout construction.

 
Since then, Diverging Diamond interchanges have been built or been considered in numerous other states, including North Carolina. As of October 2017, there are a dozen in operation. Eight others are either in the planning phase or under construction in Alamance, Cabarrus, Johnston, Mecklenburg, Randolph and Wake counties.

Diverging Diamond Interchanges in N.C.

​Interchange
​Location
I-26 at N.C. 280​Asheville​
​I-485 at Mallard Creek Road
Charlotte​
I-85 at Poplar Tent Road​Concord​
I-85 at N.C. 73​Concord​
I-77 at Catawba Avenue​Cornelius
​I-73 at High Point Road
Greensboro​
I-40 at Union Cross Road​Kernersville​
​U.S. 17 at N.C. 133
Leland​
I-95 at U.S. 301​Lumberton​
​I-40/I-85 at N.C. 119
​Mebane
U.S. 21 at I-40​Statesville​
​U.S. 52 at Salem Creek Connector
Winston-Salem​

8/6/2019 1:25 PM