West Chatham Street Roundabout

East Chatham Street Roundabout

Project Background

Modern roundabouts are circular intersections that use a rotating flow of traffic to allow safer and slower movements of traffic through intersections. All vehicles entering a roundabout must yield to vehicles already in the circulating roadway, resulting in a constant flow of traffic into and out of the circle.

Many people are not comfortable with the idea of a roundabout if they're unfamiliar with how they operate.  Some people don't want to ride in circles just to make a left-turn, or are afraid they will be stuck in the middle of the circle and never get out.  With the growing use of roundabouts in the U.S., and the abundant history that roundabouts have in Europe, drivers are becoming more aware of the advantages of roundabouts and how to use them.

Most roundabouts in Cary are single lane roundabouts, meaning they have one lane inside the circle.  There are many safety and operational advantages to single lane roundabouts either when converting an existing intersection or when constructing a new intersection.

Advantages

• Improved overall safety: Up to a 90% reduction in fatalities, 76% - 85% reduction in injury crashes and 35% - 62% reduction in all crashes.
• The design of a roundabout includes median islands and a center island that is designed to control and reduce speeds so that drivers can enter and exit the roundabout safely, with enough visual distance to react to vehicles, cyclists, and pedestrians.
• Roundabouts use crosswalks that are set back from the circulating roadway by a distance equal to about one car length.  This allows queued vehicles to leave a gap for pedestrians to use the crosswalk, and drivers don’t have to negotiate both pedestrians and circulating traffic at the same time. The medial island allows pedestrians to base their crossing on one lane of traffic at a time.

Another type of roundabout is a multi-lane roundabout. While not as common as single-lane roundabouts, they do offer safety and operational benefits just like a single-lane roundabout. The safety improvements of multi-lane roundabouts are generally not as significant as single lane roundabouts, when compared to the intersections they replace; however, multi-lane roundabouts are safer than traditional intersections.

Roundabouts are limited in their application since they cannot handle traffic at all types of intersections. Usually, intersections that handle very large volumes of traffic must rely on traffic signals to process the heavy volumes. Also, intersections that have high volumes of traffic on the main road and light volumes on the side road do not benefit from the construction of a roundabout.

Driving Roundabouts

• Slow down and watch for pedestrians
• Yield to vehicles already in the roundabout
• Once in the roundabout, you have the right of way
• Use your turn signal when exiting the roundabout and watch for pedestrians 
• Always be cautious and look for unexpected vehicles, pedestrians or bicycles

For additional information on roundabouts, please see these helpful resources:

• NCDOT's Guide to Driving Roundabouts (pdf)
• NCDOT's Inventory of North Carolina Roundabouts (pdf)
• Washington State DOT "Driving Roundabouts" website
• FHWA roundabout website

Other Helpful Links

• NCDOT Research Presentation – Safety Evaluation of Roundabouts in NC
• National Cooperative Highway Research Program Report 572 – Roundabouts in the United States

More Info

For questions or more information dial 311 within town limits, (919) 469-4000 outside Cary, or fill out an online request.