RALEIGH — City construction workers opened Raleigh's largest roundabout Monday, the city's only such traffic pattern on a major road and a milestone in the $9.9 million first phase of the Hillsborough Street renovation project.

The roundabout, which will eventually become the only two-lane one in the city, sits on Hillsborough Street near the Bell Tower at N.C. State University, where there was previously a stoplight.

An existing roundabout just south at Pullen Road and Stinson Drive opened in 2003, and a new one north on Oberlin Road opened several weeks ago.

Combined, officials say the roundabouts will help keep traffic flowing and the speed slow on busy and often congested Hillsborough Street, a primary gateway to downtown Raleigh that borders the NCSU campus.

In place of a red light or a stop sign, a roundabout pulls drivers into a counterclockwise circle, where they can exit onto side streets without stopping or crossing in front of other cars.

"It's an accomplishment," Gilbert Brown, a Raleigh senior engineering inspector, said of the Hillsborough Street roundabout. "I called everyone at City Hall yesterday when we finished."

For now, only one lane on this big roundabout is open until construction on the inside of the circle is complete, which city staffers say will be next summer. Brown said the crews are five months ahead of schedule but still have to build a small, slanted concrete edge for trucks that might hit the curb of the traffic pattern.

NCSU students and people who work on Hillsborough Street had mixed reactions to the project on Tuesday, the first full day the large roundabout was open.

Some agreed with thecity's assessment that the roundabout will result in fewer traffic jams and slower speeds, and they thought its completion would be good for business.

"It should save a lot of time and congestion," said Kyle Rogers, a junior who studies mechanical engineering. "I feel pretty optimistic about it, but we won't really be able to tell until everyone comes back next semester."

Others think that because roundabouts are rare in Raleigh and foreign to some motorists they could make Hillsborough Street more dangerous.

"People don't know how to drive on these," said Cindy Campbell, who delivers for Wing Zone. "I've seen three or four near misses out there already."

Mitchell Silver, Raleigh's planning director, said though drivers will have to adjust to the roundabouts, accident rates on them are low because they force drivers to use their senses rather than rely on traffic signals.

That seems to be true on Pullen Road.

According to Department of Transportation safety engineers, there were 12wrecks near Stinson Drive in the three years prior to the roundabout's construction. There were only three accidents in the three years after its completion.

"They needed to do something," said John Wardlaw, who sells life insurance and owns a couple of apartments above his Hillsborough Street office. "I think they've done a wonderful job."

The section with the new roundabout stretches from Gardner Street to Oberlin. It includes new street lights and sidewalks. Bike advocates are pushing the city to add bike lanes.

Brown said that section should be done by August.

ray.martin@newsobserver.com or 919-836-4952