Street Talk 101
What is a double crossover diamond (DCD) interchange?
Most interstate entrance and exit ramps are built as conventional diamond interchanges. Drivers move on and off the interstate and cycle through varying numbers of traffic signals. When making left turns, they must do so in front of oncoming traffic.
In a double crossover diamond interchange, or DCD, traffic through an interchange follows clearly-defined curbs, signs, pavement markings and state-of-the-art signals to move briefly over to the left side of the road. This eliminates the need for drivers to turn left in front of oncoming traffic. Drivers who need to continue through the interchange then cross back over to the right side of the road, leading to the “double crossover” name.
Double Crossover Diamond Interchange
Watch a brief video of how to drive through a DCD, I-75 I-71 DCD interchange at Mt.Zion Road (KY 536) in Florence, Kentucky provided by 75crossings.com
What are the benefits of a DCD?
DCDs are proven to dramatically improve safety because they eliminate numerous traffic conflict points.
Additionally, because speeds are reduced within the DCD, if crashes do happen, they are often less severe.
Because there is no need for a separate signal phase to allow for left turns, DCDs also move drivers through high traffic areas much more efficiently. DCDs are quicker and less expensive to build than many other interchange alternatives.
Why do drivers who travel through DCDs say they are simple and easy?
Driving through a DCD is very intuitive. Clear pavement markings, signs, raised medians, curbs and state-of-the-art traffic signals guide drivers all the way through the interchange.
How many DCDs are there in the United States?
Though popular in France since the 1970s, the first U.S. DCD opened in Springfield, Missouri, in 2009. Today, there are 89 DCDs across the country.
Are there other DCDs in Kentucky?
The first and only DCD interchange in Kentucky opened in Lexington at Harrodsburg Road (US 68) and New Circle Road (KY 4) in August 2011. Construction is also underway in Paducah to add a DCD at the I-24 interchange along U.S. 60. The new interchane is expected to open at the end of the year.
Abbreviated SPUI – and pronounced SPOO-EE – a Single Point Urban Interchange is an increasingly popular design to help move traffic at major interchange locations more safely and efficiently.
Most interstate entrance and exit ramps are built as conventional diamond interchanges. Drivers enter and exit the interstate by moving through multiple traffic signals.
In a SPUI, a new traffic pattern is established and opposing left turns can occur at the same time without crossing. Drivers move on separated roadways that allow for freer movement of traffic. In addition, SPUIs have only one set of traffic signals with upgraded technology that control all movement and clear pavement markings guide traffic through the interchange.
For example, an operational SPUI at Burlington Pike (KY 18) and Camp Ernst Road (KY 237) allows traffic on KY 18 to move continuously through the interchange, while traffic on KY 237 is separated from traffic on KY 18 and has one primary set of signals that control all traffic.
This innovative traffic design improves safety, eases congestion, and decreases travel times.
Traffic moves through a single point urban interchange safely and easily.
Urban Interchange (SPUI)
Roundabouts are a common intersection type that have been proven to dramatically improve safety and support better traffic flow. Rather than a traditional intersection with traffic signals, drivers moving through a roundabout do so by reducing speed and moving in one direction through a circular traffic pattern to make turning movements.
Drivers entering a roundabout must always yield to traffic that is already moving in the roundabout.
Roundabouts are recognized for easing congestion as traffic flows more continuously, as well as reducing the number and severity of traffic incidents at a given intersection. When traffic incidents do occur within a roundabout, they are often less severe as a result of slower speeds, and because traffic is moving in the same direction, the possibility of head-on collisions is eliminated.
If you are in a roundabout when an emergency vehicle approaches, immediately proceed to the nearest exit to move out of the roundabout and then proceed to a safe stop.
Watch an instructional video on how to drive safely through a roundabout.
Quick Roundabout Reminders:
Yield to drivers in the roundabout
Stay in your lane
Do not stop in the roundabout
A “jughandle” or “half loop” design is an innovative traffic
solution that is used to help ease congestion and improve safety at high-traffic intersections.
The jughandle shifts the traffic pattern by using a new road to support safer turning movements, or in some instances, diverting traffic to the new road and away from the primary intersection altogether. In addition, upgraded signals are timed to keep traffic moving more efficiently, especially during peak hours.
Major intersections are often controlled by signals that require up to four phases to accommodate left turns from each leg of the intersection. In a jughandle design, the signals at the primary intersection no longer require any phases for left turns and the signals at each end of the new road are only required to accommodate left turns during two phases. In addition, the two phases required for left turning movements at the new road are now situated at separate locations, which allows the signals to be better coordinated to move large volumes of traffic in a more efficient manner.