Changing lanes

Transportation engineers at North Carolina State University have designed a road interchange that requires less real estate, making it a good alternative for high-density urban areas where land is scarce and expensive.

Dr. Joseph E. Hummer, a professor of civil, construction, and environmental engineering, and recent master’s graduate Meredith L. Harris designed the new four-level interchange, called the ‘nanointerchange’, that saves about 10 to 30 acres of land as compared to a conventional four-level interchange.

A conventional four-level interchange accommodates all ramp speeds and consists of one freeway crossing over another, with two additional levels of connector roads that also cross. It is a common urban interchange design and can be found throughout the US.

'The four-level interchange works well, but we were interested in seeing whether we could reduce the amount of land it takes up,’ Hummer said.

Harris, as part of her graduate research, compared two versions of the nanointerchange to the four-level interchange, evaluating a number of factors, including construction costs and right-of-way requirements. She compared Hummer’s original design, the “reverse nanointerchange,” and her modification, the “parallel nanointerchange,” to the conventional four-level interchange.