Recently, I wrote an article about the merits of avoiding lefthand turns while driving. One way engineers are to address the dangers of lefthand turns is with the double crossover diamond interchange to remove the lefthand turns that cross traffic patterns and keep traffic flowing.
Prior to 2009, there were only three such interchanges, and they were all located in France. The first DCD in America was introduced by the Missouri Department of Transportation and was constructed in Springfield in 2009. The Lexington DCD at Harrodsburg and New Circle road, completed in 2011, was the 11th one in the United States. Today there are a total of 51 operational DCD interchanges throughout the country, and dozens more are in the planning or construction phase.
In Northern Kentucky where I often work, the state is looking to install a DCD at Mt. Zion Road/ I-75/I-71 and also at the Richwood Road/I-71/I-75 interchanges. In Paducah, they are looking to adding a DCD at U.S. 60 near I-24 exit.
Back in Lexington, studies are underway to add an additional DCD at the Leestown Road-New Circle Road interchange once the road widening project is complete, and the Richmond Road and Old Frankfort Pike interchanges to New Circle Road are next on the list. But how safe are they?
After enduring a lifetime of delays at the interchange on Harrodsburg Road and New Circle, I must say that the DCD works and I am impressed with the results. But I must add that when it was first introduced, it was a bit confusing to me and, I suspect, most other drivers.
That interchange was one of the most congested and dangerous multilane intersections in the city. In fact, some 35,000 cars a day traveled through there, and the left hand turns onto New Circle Road in both directions have been the scene of multiple fatalities and long delays. The sister of a high school classmate of mine was killed in this very intersection nearly three decades ago; a lefthand turn was involved.
Prior to construction, there were an average about 10.3 crashers per month from 2008-2011. The year following completion, the number of crashes dropped to 5.67 per month, which represented a 45 percent decrease. With the elimination of lefthand turns across traffic, the probability of a severe and life threatening “T-bone” accidents has been greatly diminished, and the severity of accidents have been reduced dramatically.
The Kentucky State Police Traffic Collision Facts reports from 2010 indicate accidents along Harrodsburg Road/U.S. 68 cost an average of $2 million a year in the three years prior to the DCD’s construction. Because there has been a 45 percent reduction in accidents since, drivers will save around $1 million each year, including indirect accident losses such as medical expenses and lost wages.
With a $6.24 million construction cost for the DCD, in a few years the costs savings associated with fewer accidents will exceed the cost of building the interchange; as a result, the DCD will pay for itself during its lifetime.
Additionally, traffic backups and delays have been cut in half and the flow of traffic has improved dramatically. This is amazing when you consider that the number of cars traveling through this area has increased by some 30 percent since completion, as many drivers are no longer avoiding the area. This was accomplished by increasing the capacity of an existing underpass and by removing the need for the lefthand turning lanes in both directions.
A recent survey conducted by the Kentucky Transportation Cabinet said that 72 percent of people who responded said that the design was a good solution and recommended its use elsewhere. And more than 62 percent of respondents said they agreed or strongly agreed that the stretch of Harrodsburg Road was safer.
The icing on the cake is that these DCD are far less expensive to construct than traditional road-widening options. By using existing infrastructure at the Harrodsburg Road/New Circle interchange, project costs were held to $5.5 million, as opposed to $15 million or $20 million to completely rebuild the interchange and add additional lanes. Construction took only five months to complete, verses the two construction seasons proposed to rebuild it, which minimized the impact on the traveling public. The project team was also able to provide a shared-use path that allows for pedestrians and bicyclists to safely pass through the interchange area.
The innovative and cost-saving DCD Interchange in Lexington has since been recognized by the American Association of State Highway and Transportation Officials as one of the 10 best transportation projects in the United States.
The concept of the DCD serves as proof that the best creator next to God is an engineer. It also lends credence to my core belief that all accidents can be prevented with enough commitment, intelligence and desire.
Be safe, my friends.
Keven Moore works in risk management services. He has a bachelor’s degree from University of Kentucky, a master’s from Eastern Kentucky University and 25-plus years of experience in the safety and insurance profession. He lives in Lexington with his family and works out of both the Lexington and Northern Kentucky offices. Keven can be reached at kmoore@roeding.com.