The N.C. Department of Transportation plans to remake the Interstate 40 interchange at Airport Boulevard and wants the public’s help in deciding how.
The NCDOT is weighing two options: a partial-cloverleaf similar to what’s there now, and a relatively new kind of design called a diverging diamond, or DDI. There are no diverging diamonds in the Triangle yet, but several are being considered, because traffic engineers say they are generally safer and keep traffic moving better than traditional designs.
In this case, the two designs would move traffic equally well, says Bob Deaton, the project manager for DOT. But Deaton says the diverging diamond has the added advantages of requiring less real estate and allowing the existing bridge to remain in place while two parallel bridges are built.
“Internally, we’re leaning a little bit toward the DDI,” Deaton said. “But if for some reason the public came back and really didn’t like it, or if something else comes up, we’re fine with the partial clover as well.”
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The NCDOT will present the two plans at a public meeting at the LaQuinta Inn and Suites at 101 Hospitality Court near the interchange on Tuesday, Jan. 30. There will be no formal presentation, but the public can stop in anytime between 4 and 7 p.m. Those who can’t attend can share their thoughts on the project by email to firstname.lastname@example.org.
The Airport Boulevard bridge over I-40 was built in 1971 when Morrisville was still a rural community between Cary and a still-fledgling Research Triangle Park. NCDOT wants to replace the interchange with a wider bridge and a more thoughtful design to reduce traffic congestion that has gotten worse over the years, Deaton said.
“It’s a very busy interchange in a very busy part of town,” he said.
Both of the proposed interchange designs would relieve traffic in part by eliminating left-hand turns by vehicles coming off the interstate. The diverging diamond goes further by also eliminating all left-hand turns across traffic by crisscrossing the lanes at traffic signals at each end of the bridge over the highway.
Diverging diamonds can appear daunting at first, but people who have navigated them in other parts of the country say they are a lot less confusing than they look on paper.
Construction is not expected to begin until late 2019 and would not be completed until late 2021 or early 2022.
Meanwhile in April, contractors will begin a similar reconstruction of the I-40 interchange at Aviation Parkway. The $21.4 million project will include a new loop ramp from westbound I-40 onto southbound Aviation that will eliminate a left-hand turn. The new interchange is expected to be completed by September 2020.
The new bridges at Aviation Parkway and Airport Boulevard will be longer, to accommodate more lanes on I-40 should local transportation planners and the state ever want to widen it. The bridges will be long enough for two additional lanes on either side of the highway, which would make I-40 a total of 12 lanes wide.