Best Highway/Bridge: Engineers Take Different Approach for Unique N.C. Interchange
Charlotte’s Interstate-485 Outer Loop, one of the state’s most vital urban interchanges, links I-77 to I-85 as well as other major arterials. In 2010, the North Carolina Dept. of Transportation (NCDOT) initiated a design-build-finance advertisement for the $124-million interchange modification as part of the agency’s effort to close the last six-mile gap of the newly constructed I-485 outer loop to the north. The project’s scope included the reconstruction of the existing I-485/I-85 interchange into a fully directional four-legged interchange.
During the RFP phase, the design-build team of contractor Lane Construction Corp. and engineer STV proposed replacing the four-level stack with a two-level turbine interchange, a configuration rarely seen in the U.S. Lane/STV concluded that the turbine layout—also called a “whirlpool” exchange—could enhance safety for both motorists and construction workers. The design choice—never before used on a U.S. interstate highway—also significantly lowered the project’s cost, earning Lane/STV’s unique proposal a “best value” determination from NCDOT.