Roundabouts: What You Should Know

News posted Sep. 27, 2018 - 6:00 am
Hillsborough Street roundabout, Dixie Trail and Friendly Drive

What is a Roundabout?

The roundabout is a circular intersection where drivers travel in a counterclockwise pattern around a center island. The driver yields to traffic in the roundabout and then enters the roundabout and exits at the desired street. There are no traffic signals in the roundabout, making travel flow at a steady pace.

Studies conducted by the Federal Highway Administration have found that roundabouts can increase traffic capacity between 30 to 50 percent compared to traditional intersections. Increased capacity at roundabouts is due to the continuously flowing nature of yielding until a gap is available, versus waiting at a traffic signal. Roundabouts actually help you get through traffic more efficiently and safely in high traffic areas.

A Roundabout is not a Traffic Circle

Traffic circles (also called rotaries) are frequently found on the east coast and in Europe. The traffic circle is larger than the roundabout and normally includes stop signs or traffic signals that will stop traffic inside the circle. Dupont Circle in Washington, DC, is an excellent example of a traffic circle. Drivers enter a traffic circle straight on with a stop sign or traffic signal. Traffic circles can become congested if traffic signals allow too many vehicles to enter at the same time.

Vehicles enter the roundabout at a soft right turn, yielding to traffic already in the roundabout. This action allows for a smooth transition making it rare for a roundabout to get congested.

Features of the Modern Roundabout

When approaching the roundabout vehicular traffic will encounter triangular splitter islands, designed to slow and guide traffic. The islands direct traffic to the right providing a soft right entrance to the roundabout, which helps to reduce the amount of T-bone or head-on collisions. The islands provide refuge for pedestrians, letting them cross one direction of traffic at a time and have a safe place to wait before crossing another direction of traffic. It is important to note that pedestrians have the right of way at these crosswalks.

The roundabout’s main physical feature is the raised central island, designed to control the direction of traffic and reduce the speed of traffic to 20 miles per hour or less. In Raleigh, the center island of a roundabout includes a truck apron. A truck apron is a raised section of concrete that acts as an extra lane for large vehicles. The back wheels of oversized trucks can ride up on the apron, so it can easily complete the turn, while the raised portion discourages use by smaller vehicles.

Tips for Driving in a Roundabout

  • Slow down. Obey traffic signs;
  • Yield to pedestrians and bicyclists as you approach the roundabout;
  • Yield to traffic on your left already in the roundabout;
  • When there is a gap in the traffic enter to your right;
  • Keep your speed low within the roundabout;
  • As you approach your exit, turn on your right turn signal; and,
  • Yield to pedestrians and bicycles as you exit.

Emergency vehicles in the roundabout

  • Always yield to emergency vehicles;
  • If you have not entered the roundabout, pull over and allow emergency vehicles to pass;
  • If you have entered the roundabout, continue to your exit, then pull over and let emergency vehicles pass; and,
  • Avoid stopping in the roundabout.

Safety features of single-lane roundabouts

Roundabouts are designed to make intersections more efficient and safer for drivers, pedestrians and bicyclist.

Roundabouts reduce vehicle speed utilizing geometry rather than traffic signals or traffic volume, making it possible to reduce speeds consistently.

Low-speed Benefits:

  • Reduces crash severity for motor vehicles, pedestrians, and bicyclists (pedestrians are three times more likely to die when struck at 30 mph tan 20 mph);
  • Reduces conflict points;
  • Reduces conflict severity; and,
  • Reduces vehicle speed.

Environmental Factors:

  • Reduces noise, air quality, and fuel consumption by reducing the number of stop and go cycles and time spent idling (most of the time); and,
  • Operation and maintenance costs are lower than traffic signals.

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