NPR for Northern Colorado
Play Live Radio
Next Up:
Available On Air Stations

Cutting Edge Diverging Diamond Interchanges Coming To Colorado

Traffic flow patterns on the new I-70 DDI in Grand Junction

Construction on the state’s first diverging diamond interchange is nearly complete in Grand Junction. The innovative project will open sometime in April. The Colorado Department of Transportation says it will give drivers freeflow access to a left hand I-70 on-ramp without having to wait for a traffic turn signal, or turn into on-coming traffic.

Diverging diamond interchanges, or DDI, are a relatively new traffic management tools in the United States. The first DDI opened along Missouri’s Interstate 44 corridor in 2009. According to divergingdiamond.com there are 34 DDI’s nationwide.

CDOT says the new interchange will help ease congestion:

A DDI eliminates traditional left-hand turns by crossing lanes and shifting drivers to the left side of the road. This gives drivers direct access to a left-hand ramp to access the interstate without waiting at a traffic signal. The lanes then shift drivers back to the right side.

How a Diverging Diamond Interchange works.


According to CDOT and the city of Grand Junction, the new DDI can handle 650 left hand turns an hour, twice the amount of a normal interchange. And with fewer traffic signal changes (two instead of the typical four) traffic will flow smoothly through the interchange without the need for additional lanes.

CDOT says the cost to build a traditional ‘cloverleaf’ interchange at the exit 26 interchange was approximately $10 to $15 million. The DDI has a construction cost of $4 million.

While a DDI does have its advantages, it isn’t perfect. Besides being potentially confusing, motorists who take the wrong exit aren’t able to cross the intersection and get back onto the interstate, they’ll have to pass through the interchange, turn around, and proceed through it again to get back onto the highway.

A Driver’s View of a Diverging Diamond Interchange


While the DDI in Grand Junction will be the first to open in the state, it won’t be the only one. CDOT is planning 2 more. One is slated to open next year on U.S. 36 at McCaslin Blvd in the town of Superior, and another is on the books, but not yet under construction, at I25 and Fillmore Street in Colorado Springs.

Related Content