Traffic

'Super circles' set drivers', traffic planners' minds spinning

Posted August 8, 2013 5:46 p.m. EDT
Updated August 8, 2013 6:53 p.m. EDT

— With more people moving to the Triangle, area transportation planners are looking for ways to ease congestion with limited funding.

One idea being studied is a "super circle," which some consider a roundabout 2.0.

Roundabouts, such as those on Hillsborough Street in Raleigh and those being constructed on Chatham Street in Cary, require entering cars to yield to those already in the circle. Transportation engineers say they are generally more efficient and safer than intersections controlled by red lights because cars usually aren't stopped for long periods and are moving at a much slower speed.

Still, roundabouts draw mixed reviews from area drivers.

"I think, if you understand the rules and the process, it keeps the traffic flow consistent," driver Darin Sensabaugh said.

"To me, (drivers are) more likely to hit somebody than when it was straight through and you had to pay attention to the red lights," driver Dayle Conover said.

A "super circle" involves adding one stop light to a roundabout to control the number of vehicles entering during rush hours.

"That would only operate during the peak hour or two when we need it, but the idea there is that signal on the one approach, when it turns red, it frees up space in the circle," said Joe Hummer, a former North Carolina State University professor who is now a traffic engineer at Wayne State University in Detroit.

Super circles are big in Australia, but Maryland and Florida are the only locales in the U.S. that have any, Hummer said. Triangle planners asked him to examine the idea, and he said they could replace some traditional intersections in the area.

"We didn't think a roundabout was possible, and now it will be," he said. "There's really lots of those (intersections) out there – one-lane streets or two-lane streets, the moderate volume."

Hummer acknowledged that American drivers generally haven't adapted to roundabouts, but he said he expects that will change as more drivers get used to them.

"It sounds like there's been an engineer hard at work that he's analyzed the situation pretty thoroughly," Sensabaugh said. "I could see where that would work out."