Research, Development, and Technology Turner-Fairbank Highway Research Center 300 Georgetown Pike, McLean, VA 22101-2296

www.tfhrc.gov

Double Crossover Diamond Interchange

Objective

Today’s transportation professionals, with limited 

resources available to them, are challenged to 

meet the mobility needs of an increasing population. At many highway junctions, congestion 

continues to worsen, and drivers, pedestrians, 

and bicyclists experience increasing delays and 

heightened exposure 

to risk. Today’s traffic

volumes and travel

demands often lead

to safety problems

that are too complex

for conventional interchange designs to

properly handle. Consequently, more engineers are considering various innovative treatments as they

seek solutions to these

complex problems. 

The corresponding technical report, Alternative

Intersections/Interchanges: Informational

Report (AIIR) (FHWAHRT-09-060), covers 

four intersection designs and two interchange designs that offer 

substantial advantages

over conventional atgrade intersections and

grade-separated diamond interchanges. The

AIIR provides information on each alternative 

treatment covering salient geometric design features, operational and safety issues, access management, costs, construction sequencing, environmental benefits, and applicability. This TechBrief 

summarizes information on one alternative interchange design—the double crossover diamond 

(DCD) interchange (see figure 1).

Figure 1. First U.S. DCD interchange at I-44 and Route 13 in Springfield, MO.

FHWA Publication No.: FHWA-HRT-09-054

FHWA Contact: Joe Bared, HRDS-05, (202) 493-3314, joe.bared@dot.gov

This document is a technical summary of the Federal Highway Administration 

report, Alternative Intersections/Interchanges: Information Report (AIIR)

(FHWA-HRT-09-060).

TECHBRIEF

 Source: Missouri Department of Transportation
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Introduction

The DCD interchange, also known as a diverging 

diamond interchange (DDI), is a new interchange 

design that has much in common with the design 

of a conventional diamond interchange. The main 

difference between a DCD interchange and a 

conventional diamond interchange is in the way 

left and through movements navigate between 

the cross street intersections with ramps (see 

figure 2). The DCD design accommodates leftturning movements onto arterials and limitedaccess highways while eliminating the need for 

a left-turn signal phase at signalized ramp terminal intersections. On the cross street, the traffic 

moves to the left side of the roadway between 

the signalized ramp intersections. This allows drivers of vehicles on the cross street who want to 

turn left onto the ramps the chance to continue 

to the ramps without conflicting with opposing 

through traffic and without stopping. 

Several DCD interchanges have been built in 

France, including the intersection of Highway A13 

and RD 182 (Boulevard de Jardy) in Versailles, the 

intersection of Highway A4 (Boulevard des Allies) 

and Boulevard de Stalingrad in Le Perreux-surMarne, and the intersection of Highway A1 and 

Route d’Avelin in Seclin. In the United States, the 

first DCD interchange was completed in July 2009 

in Springfield, MO, at the intersection of Route 13 

and I-44 (see figure 1). Several other DCD interchanges are being planned, including the intersection 

of I-435 and Front Street in Kansas City, MO.

Geometric Design

The primary elements of a DCD interchange design 

are as follows:

•	 Left-turn and through movements are relocated to the opposite side of the road on the 

bridge structure. Turning radii used at the 

crossover junction are typically in the 150- to 

300-ft range.

•	 Median width is increased to allow for the 

flaring required for reverse curves on the 

interchange approaches.

•	 The skew angle between the intersecting 

directions is closer to perpendicular when 

possible.

•	 Median openings are placed upstream of the 

interchange to allow U-turn movements on 

the arterial roadway. 

“Crossed-over” through and left-turn 

movement in one direction on arterial

“Crossed-back” through movement in one 

direction on arterial

Right-turn movement onto freeway on-ramp

Signal-controlled crossovers

Unopposed left-turn movement onto 

freeway on-ramp

Signal-controlled off-ramp

Figure 2. Crossover movement in a DCD interchange.

Freeway

Freeway
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•	 Pedestrian crossings are accommodated 

by installing crosswalks and signalization at 

the junctions or nodes of the interchange (see 

figure 3). The two-phase signal control possible in a DCD is more efficient for pedestrians, but it requires them to cross the junction 

in two stages with the central island serving

as a refuge between signal phases. Additionally, pedestrians could have the option 

to walk in the median of the DCD interchange (implemented for the DCD interchange 

at the junction of I-44 and Route 13 in 

Springfield, MO).

Traffic Signal Control

A DCD interchange typically has two signalized 

junctions or nodes at the points of left-turn crossovers. The signals operate with just two phases, 

with each phase dedicated to the alternative 

opposing movements. The two-phase operation of 

a DCD interchange allows for shorter cycle lengths 

and reduced lost time per cycle compared to the 

three- or four-phase operation at conventional 

diamond interchanges. Signals on a DCD interchange may be fully actuated to minimize delay, 

and both signalized junctions can be operated 

using either one or two controllers.

Operational Performance

The traffic simulation software VISSIM was used 

to compare the operational performance of DCD 

interchanges to conventional diamond interchanges. Two DCD interchange designs and two 

conventional diamond interchange designs were 

simulated under high and low traffic volumes. 

At the higher traffic volume simulations, the DCD 

interchange demonstrated overall better performance. It had less delays, fewer stops, reduced 

stop times, and shorter queue lengths compared 

to the conventional design. Delays were reduced 

by 15 to 60 percent, and throughput was increased 

by 10 to 30 percent. However, at lower volumes, 

the performance of the DCD interchange and 

conventional diamond interchanges were similar.

The simulation showed that service volumes of 

left-turn movements (650 vehicles per hour per 

lane (veh/h/lane)) could be twice that of the 

corresponding left-turn service volumes of a 

conventional diamond. An advantage of the DCD 

interchange over the conventional diamond is 

that exclusive left-turn lanes are not necessary for 

the DCD interchange.

Figure 3. Typical DCD interchange movements.

Side Street

Freeway

Freeway Ramps Freeway Ramps

Pedestrians
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Researchers—This study was performed by Principal Investigators Warren Hughes and Ram Jagannathan. For 

more information about this research, contact Joe Bared, FHWA Project Manager, HRDS-05 at (202) 493-3314, 

joe.bared@dot.gov.

Distribution—This TechBrief is being distributed according to a standard distribution. Direct distribution is being 

made to the Divisions and Resource Center.

Availability—This TechBrief may be obtained from the FHWA Product Distribution Center by e-mail to 

report.center@dot.gov, fax to (814) 239-2156, phone to (814) 239-1160, or online at http://www.tfhrc.gov/safety.

Key Words—Diverging diamond interchange, DDI, Alternative interchange, Double crossover diamond, and DCD.

Notice—This document is disseminated under the sponsorship of the U.S. Department of Transportation in the 

interest of information exchange. The U.S. Government assumes no liability for the use of the information contained 

in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ 

names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high-quality information to 

serve the Government, industry, and public in a manner that promotes public understanding. Standards and policies 

are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically 

reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Safety Performance

A DCD interchange has only 14 conflict points 

and two crossing points. In comparison, a conventional diamond interchange has 26 conflict 

points. Missouri Department of Transportation 

designers noted that the DCD interchange geometry also has traffic calming features that reduce 

speeds while maintaining capacity. This is expected 

to result in fewer and less severe crashes than in 

a conventional intersection. They also noted that 

the shorter clearance distances on the DCD interchange ramps compared to an equivalent conventional diamond interchange could result in 

reduced vehicle exposure times within the 

intersection and thereby lead to improved safety. 

Another noted feature of a DCD interchange is that 

wrong-way movements onto ramps are eliminated.

Applicability

The main reasons to choose a DCD interchange 

design instead of a conventional interchange 

design include traffic operational benefits, potential 

safety benefits, right-of-way benefits, and reduced 

construction costs. DCD interchanges are especially 

suitable in suburban/urban settings where limited and costly right-of-way and reduced duration 

of construction are critical issues. Environmental 

benefits have not yet been estimated, but it is clear 

that the reduced congestion and possible safety 

benefits will result in reduced fuel consumption 

and pollution. Some situations where DCD interchanges are most applicable are as follows:

•	 Heavy volumes of left turns onto freeway ramps.

•	 Moderate and unbalanced through volumes 

on bridge approaches on the arterial road.

•	 Moderate to very heavy off-ramp left-turn 

volumes.

•	 Limited bridge deck width availability.

Summary

The DCD interchange offers benefits over conventional interchange designs with its efficient 

two-phase operation, narrower bridge structure width, lower costs, fewer conflict points, 

expected increase in throughput, reduced vehicular delay, decreased speeds, and reduced environmental impact. At this time, there is one existing 

DCD interchange site in the United States and 

three DCD interchanges in France. Other State 

transportation departments have initiated and 

planned the construction of several additional 

DCD interchanges. More details on DCD interchanges and other innovative intersection designs 

can be found in the full AIIR available from the 

Federal Highway Administration.

october 2009 FHWA-HRT-09-054

HRDS-05/10-09(3M)E