Roundabouts

What are Roundabouts?

Roundabouts are circular, unsignalized intersections in which vehicles travel counterclockwise around a center island until they reach their intended exit. Traffic entering the roundabout yields to circulating traffic, which has the right-of-way.

What are the Benefits of Roundabouts?

• Safety
  • Studies have shown roundabouts can reduce crashes, with significant reductions in injury and fatal crashes.
  • Necessitate slower speeds (15-20 mph).
  • Eliminate left turns across traffic at the intersection.
• Operational
  • Cars all move in the same direction (stop-and-go nature is reduced) to improve traffic flow.
  • Roundabouts can accommodate similar traffic volumes as two-way stop, four-way stop, and signal-controlled intersections with less delays and shorter queues.
• Economic
  • Eliminate installation and operational costs for traffic signals.
  • Reduce maintenance. Intersections still operate during power outages without additional resources.
• Environmental
  • Reduce pollution, noise, and fuel consumption due to fewer stops/accelerations and less idling.
  • Center islands can be landscaped with native trees and plants.
  • Occupy less land than traditional intersections because turning lanes aren’t required.

What Considerations Should be Made When Designing Roundabouts?

• The roundabout’s geometric parameters.
• Single- or multi-lane roundabout—best to construct only what’s needed for current traffic needs.
• Expandable design.
• The surrounding area—speed limit, average traffic flow, and potential impacts to properties.
• Accommodating emergency and oversize vehicles.