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RALEIGH, N.C. — The so-called “superstreet” traffic design results in significantly faster travel times and leads to a drastic reduction in automobile collisions and injuries, according to North Carolina State University researchers who have conducted the largest-ever study of superstreets and their impacts.

Superstreets are surface roads, not freeways. They are defined as thoroughfares where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. While this may seem time-consuming, the study shows that it actually results in a significant time savings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare.

“The study shows a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs,” said Joe Hummer, Ph.D., professor of civil, construction, and environmental engineering at North Carolina State University and one of the researchers who conducted the study. “We also found that superstreet intersections experience an average of 46 percent fewer reported automobile collisions — and 63 percent fewer collisions that result in personal injury.”

The researchers assessed travel time at superstreet intersections as the amount of time it takes a vehicle to pass through an intersection from the moment it reaches the intersection — whether traveling left, right, or straight ahead. The travel-time data was collected from three superstreets located in eastern and central North Carolina, all of which have traffic signals. The superstreet collision data was collected from 13 superstreets located across North Carolina, none of which have traffic signals.

The superstreet concept has been around for more than 20 years, but little research had been done to assess its effectiveness under real-world conditions. The North Carolina State University study is the largest analysis ever performed of the impact of superstreets in real traffic conditions.

A paper on the travel time research is being presented Jan. 24 at the Transportation Research Board Annual Meeting in Washington, D.C. The paper is co-authored by Hummer, former North Carolina State University graduate students Rebecca Haley and Sarah Ott, and three researchers from the university’s Institute for Transportation Research and Education: Robert Foyle, associate director; Christopher Cunningham, senior research associate; and Bastian Schroeder, research associate.

The collision research was part of an overarching report of the study submitted to the North Carolina Department of Transportation (NCDOT) last month, and is the subject of a forthcoming paper. The study was funded by NCDOT.