http://safety.fhwa.dot.gov

SOURCES

1 FHWA, Techbrief: Double Crossover Diamond Interchange, FHWAHRT-09-054 (Washington, DC: 2009). Available at: https://www.

fhwa.dot.gov/publications/research/safety/09054/index.cfm

2 Missouri DOT, Diverging Diamond Interchange Performance 

Evaluation (I-44 and Route 13), OR11-012 (2011). Available 

at: https://ntlrepository.blob.core.windows.net/

lib/36000/36000/36038/or11012.pdf 

3 Praveen Edara, Joe Bared, and Ram Jagannathan, “Diverging 

Diamond Interchange and Double Crossover Intersection – Vehicle 

and Pedestrian Performance,” Transportation Research Record 1912 

(2005):31-38

4 The Official Website of the DDI - “A Diamond Interchange With a 

Twist.” Available at: https://divergingdiamond.com/

5 Missouri DOT, Diverging Diamond Interchange Performance 

Evaluation (I-44 and Route 13), OR11-012 (2011). Available at:

https://trid.trb.org/view/1098716

AN INNOVATIVE,

PROVEN SOLUTION FOR 

IMPROVING SAFETY AND 

MOBILITY AT INTERCHANGES

CONTACT

Jeffrey Shaw, P.E.

FHWA Office of Safety

202.738.7793

jeffrey.shaw@dot.gov

Mark Doctor, P.E.

FHWA Resource Center 

404.895.6210

mark.doctor@dot.gov

Trucks Using a DDI in Salt Lake County, UT

Source: DDI Video FHWA-SA-14-019

ability of trucks to turn on to and off of the ramps 

and navigate along the crossroad is not inhibited with 

a DDI. In surveys of commercial drivers using the 

Springfield (Missouri) DDI, 83 percent of respondents 

felt that maneuvering a large truck through the 

interchange was easy and no different from other 

interchange types.5

A TIMELY, COST-EFFECTIVE 

SOLUTION 

A DDI can cost less – in some cases as much as 

75 percent less – than an equivalent conventional 

diamond or single point urban interchange.4

 DDIs 

often require fewer lanes than a conventional 

design to handle the same amount of traffic. A 

smaller project footprint means less right-of-way 

is needed, resulting in fewer impacts to adjacent 

areas. All of this makes a DDI alternative cheaper, 

easier, and quicker to construct.

INTEGRATING ALL USERS 

The benefits of a DDI are not limited to just vehicle 

traffic – safe and convenient pedestrian walkways 

and crossings are important components of any 

well-designed interchange. At a DDI, pedestrian 

walkways are located either through the median 

or along the sides of the crossroad, while bicycle 

lanes are placed in the customary location to the 

right of traffic. Crosswalks are simpler and involve 

crossing fewer lanes at a time.

Given the importance of freight movement 

through interchanges, a DDI also is designed to 

accommodate large commercial vehicles. The 

Center Pedestrian Refuge, Springfield, MO DDI

Source: DDI Video FHWA-SA-14-019

FHWA-SA-14-039 Revised July 2020

DIVERGING DIAMOND 

INTERCHANGE

Atlanta, GA DDISource: Google Earth
Springfield, MO DDI

Source: DDI Video FHWA-SA-14-019

from the first year after construction to the 5-year 

average before the DDI, and found the following:

• Left turn crashes were totally eliminated.

• Right angle crashes were reduced 72 percent.

• Rear end crashes were reduced 29 percent.

• Total crashes were reduced 46 percent.2

A separate study comparing DDI designs to 

conventional diamond interchange designs 

modeled a range of high and low traffic volume 

combinations.3

 For higher traffic volumes, the DDI 

designs demonstrated better overall performance, 

reducing delay by 15-60 percent and increasing 

throughput by 10-30 percent. The DDI was able 

to accommodate twice the left turn traffic as the 

conventional design.

Opened in 2009, the DDI in Springfield (Missouri) 

was the first in the United States. Since then, dozens 

more have been built in several states, and they 

have quickly become a popular interchange design 

option. Where they have been built, travelers save 

time, agencies saved money, and communities will 

benefit from safer facilities for many years.

The crossover intersections are what make 

DDIs different, and they are very intuitive for 

the driver. The crossovers gently transition – or 

diverge – traffic from the right side of the road 

to the left side of the road and then back again. 

Because traffic is on the left hand side between 

the crossovers, all left turns occur without having 

to cross opposing traffic. The road geometry, 

signs, and pavement markings all work together 

to make this very simple. In cities where DDIs have 

been built, drivers say they don’t even notice the 

crossover intersections.

Diverging Diamond Interchanges are almost 

always worth considering as an alternative, but 

particularly if a location has any of the following 

characteristics:

• Heavy volumes of left turns on to and off of

freeway ramps.

• Moderate but unbalanced crossroad traffic

volumes through the interchange.

• Left turn related safety concerns at the

interchange intersections.

• A need for additional capacity without

widening the roadway and bridge(s).1

IMPROVING SAFETY WHILE 

INCREASING THROUGHPUT

A potential conflict exists each time a vehicle, 

pedestrian, or bicycle crosses or turns across the 

path of another direction of traffic. Compared 

to a conventional diamond interchange, the DDI 

reduces vehicle-to-vehicle conflict points by 

nearly 50 percent and eliminates many of the 

most severe crash types. An evaluation of the 

Springfield (Missouri) DDI compared crashes 

Motorists, pedestrians, and bicyclists face 

greater mobility challenges and safety risks 

at interchanges as traffic volumes grow and 

congestion worsens. Agencies need safer, more

balanced designs that keep people moving. 

Innovative intersection designs represent 

a solution, and are being built more often 

because they can deliver more for less.

WHAT IS A DIVERGING 

DIAMOND INTERCHANGE?

The Diverging Diamond Interchange (DDI) is a 

simple design innovation that improves safety and 

mobility, often at a much lower cost, compared 

to conventional interchange designs. The key to 

what makes a DDI work so well is how left turns are 

handled. 

The DDI resembles a conventional diamond 

interchange, which is the most common form in the 

United States. Drivers make right turns at a DDI just 

as they would at a regular diamond interchange.

A DDI is sometimes

referred to as a Double 

Crossover Diamond (DCD)