Completing the final sections of the 540 loop road around Raleigh will mean building what could be the largest and most complicated highway interchange in the Triangle.
N.C. 540, the Triangle Expressway, will meet Interstate 40 south of Garner at the spot where the U.S. 70 Bypass now splits off heading east into Johnston County. That will create a confluence of three interstate-grade highways at an interchange that will cover some 650 acres, an area more than two times the size of Raleigh’s Dix Park.
To make the design more challenging, the Triangle Expressway is a toll road, and N.C. Department of Transportation engineers have included separate exit ramps from I-40 to make sure drivers don't accidentally get on it.
The design they came up with looks like nothing in the Triangle now. It’s dominated by a large exit and entrance ramp connecting I-40 and N.C. 540 that will circle where the five legs of the highways meet. A rendering of the interchange elicited a wave of murmurs when it was flashed on the big screen at a public hearing at Wake Tech Community College last month.
The interchange is a custom design, chosen from several versions that NCDOT engineers sketched out. They could not simply copy one from elsewhere, because they needed to work with the I-40/U.S. 70 interchange that is already there, said Roy Bruce, the senior project manager for the project, which NCDOT calls Complete 540.
Bruce said it makes sense for the Triangle Expressway to cross I-40 at this spot, so that traffic to and from Eastern North Carolina can move seamlessly between N.C. 540 and U.S. 70.
"It gives us continuity," he said.
There will be some tight loop ramps, including the existing one from westbound U.S. 70 onto eastbound I-40. But many of the other ramps, including the big circular one, are large enough that drivers can go 55 mph from one highway to the next.
N.C. 540 will come over the top of the two existing roads, so at some points there will be three levels of highway. But with I-40 already depressed here, and the large circular ramp system to spread things out, there will be no soaring ramps like those seen in urban areas such as Los Angeles or suburban Washington, D.C. At its highest point, N.C. 540 will be 45 feet above I-40, Bruce said.
"It is relatively flat," he said.
And while it's difficult to follow your path through the tangle of loops and ramps on paper, drivers won't find it nearly so confusing, said Rodger Rochelle, the N.C. Turnpike Authority's chief engineer.
“It looks complicated when we look down on a map, but it’s actually going to be pretty simple for the driver,” Rochelle said.
The interchange is part of the final 28.4 miles of N.C. 540 that will connect Holly Springs with U.S. 64/264 near Knightdale. The Final Environmental Impact Statement, a report that spells out the possible effects of the project on the natural and human environment, was released Dec. 22, putting the state on a schedule to begin buying property this summer and starting construction early next year.
The state already owns 450 of the 650 acres needed for the interchange. The additional 200 acres will include five houses on a secluded dead-end section of New Bethel Church Road that will disappear.
The road is expected to cost $2.24 billion to design and build; NCDOT has not determined a separate price for the big interchange.
The final designs will be done by contractors chosen to build the road. Rochelle and they may come up with something different for the big interchange, as long as it achieves the same results with the same or less real estate and environmental impacts.
“Other than that, we’re open to other ideas," he said. "We think we’ve got a good solution, but we would be remiss if we said we had the best solution.”
For more information about Complete 540, go to www.ncdot.gov/projects/complete540/.