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.

Why Choose raSmith as Your Roundabout Planning, Traffic Analysis, And Design Experts?

raSmith is an industry leader in roundabouts, having successfully designed more than 150 roundabouts of various scale and complexity for state and local government since 2004.

Our transportation design team is a strong advocate for roundabouts based on their ability to improve traffic flow and safety at intersections. We have conducted many presentations on the benefits of roundabouts and design considerations to professional societies, county boards, and city councils. We have also provided roundabout design training to other consultants as well as designers in state and local government. Four of raSmith’s engineers are included on the Wisconsin Department of Transportation (WisDOT) Qualified Roundabout Designer list.

raSmith’s breadth of roundabout experience provides us with insight into finer details related to important elements such as:

  • Properly sizing and positioning the roundabout to minimize impacts to surrounding properties and wetlands.
  • Accommodating emergency services vehicles and standard semi trucks for all turn movements.
  • Accommodating oversize and/or specialty trucks.
  • Addressing lighting needs.
  • Designing with long-term maintenance in mind such as snow plowing and central island plantings.

Roundabout Services

  • Single-and multi-lane roundabouts
  • Roundabout interchanges
  • Series of roundabouts
  • Oversize truck accommodations
  • Roundabout feasibility and operation analyses
  • Project communication and public involvement
  • 3D renderings for municipal approvals and public education

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