This design allows for vehicles to turn left onto and off freeway ramps without stopping or crossing opposing lanes of traffic. Right turns on and off freeway ramps occur either before or after the crossover intersections.
A DCD can be either an overpass or underpass depending on need.
Clear lane markings and signage at DCDs help safely guide motorists through the interchange, even those who are inexperienced in driving through DCDs.
A DCD is also known as:
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A Diverging Diamond Interchange (DDI)
When to use a DCD
DCDs should be used to reconfigure conventional intersections that have high traffic volumes and crash frequencies and need a cost-effective solution.
Benefits
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Safety — DCDs reduce wrong-way entries to ramps, the number of times opposing traffic crosses paths and the potential number of crash points for vehicles. They also reduce speeds, so if crashes do occur then they are less severe.
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Efficiency — DCDs operate with fewer traffic signal phases, which increases the volume of traffic and decreases delays. The design also provides motorists with easier access to the highway without having to cross opposing traffic.
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Cost effective – Rather than building new lanes or bridges, a DCD design can improve traditional interchanges by reconfiguring existing lanes and intersections at a lesser cost.
How to use a DCD
Motorists on the main road turning right within a DCD, merge onto a freeway ramp just like a conventional interchange. Motorists on an exit ramp also turn and merge right like at a conventional interchange.
Motorists on the main road traveling straight or turning left within a DCD, follow lane markings and traffic signals to cross to the left side of the main road. They can then turn left onto the freeway ramp or cross back over to the right side of the main road to continue to travel straight through the intersection.
When turning left from an exit ramp, motorists stay on the left side of the main road and travel through the intersection before moving to the right side of the main road.
Pedestrians will encounter multiple marked crosswalks and can use them to safely navigate the interchange.
Cyclists, depending on their level of comfort, may navigate the intersection using designated vehicles and/or pedestrian paths if those are offered.
DCDs in Kentucky
U.S. 60 at Interstate 24 Exit 4 in Paducah McCracken County
The Double Crossover Diamond (DCD) interchange along U.S. 60 at Interstate 24 Exit 4 in Paducah was completed in 2019. The interchange serves a high-traffic area that provides motorists with access to a wide range of restaurants, retail stores, and Paducah's mall. At the time, it was the first innovative intersection of its kind in District 1 and only the second DCD built in the state. Since then, more DCDs have been constructed across the state.
A comparison of crash reports from the five years prior to construction to the five years after shows the U.S. 60 DCD has successfully reduced crashes while improving traffic flow along the corridor, which includes the intersections at New Holt Road and Coleman Road. The data shows:
- Collisions involving injuries dropped by 28.5%
- Total injuries fell by 32.4%
- Overall collisions decreased by 3.0%
Graves Road Boone County
