The single-land roundabout design balances the need to provide proper roadway geometry while minimizing impacts to adjacent sensitive areas. The central island will be landscaped and raised approximately 3 to 6 feet above the roadway to alert approaching drivers of the roundabout. The roundabout is sized to accommodate a WB-62 truck and trailer design vehicle while still maintaining low operating speeds recommended for a single-lane roundabout. A cement concrete, mountable truck apron is located on the inside of the circulating lane to accommodate the off-tracking of the design vehicle. 

Click here to see the project's design plans.

The roundabout will have a small diameter (22-feet) planting area, and it will be planted with low-growing shrubbery.

Crash data is collected at the beginning of the project. Information is taken from three sources: Clark County Department of Public Works, Clark County GIS data files, and the Washington State Department of Transportation. The data was collected over a five-year period (January 1, 2015, to December 31, 2019) before the design of the project. Over the five-year period, a total of eleven crashes were reported at the study intersection, including angle, turning, and fixed object collisions.

Roundabouts keep traffic moving safely and steadily. Studies have shown that roundabouts are safer than stop sign or signal-controlled intersections. Roundabouts reduced injury crashes by 75 percent at intersections where stop signs or signals were previously used for traffic control, according to a study by the Insurance Institute for Highway Safety (IIHS). Studies by the IIHS and Federal Highway Administration have shown that roundabouts typically achieve:

• A 37 percent reduction in overall collisions.
• A 75 percent reduction in injury collisions.
• A 90 percent reduction in fatality collisions.
• A 40 percent reduction in pedestrian collisions.

There are several reasons why roundabouts help reduce the likelihood and severity of collisions:

• Low travel speeds: Drivers must slow down and yield to traffic before entering a roundabout. Speeds in a roundabout are typically between 15 and 20 mph. The collisions that occur in roundabouts are typically minor and cause fewer injuries since they occur at lower speeds.
• No light to beat: Roundabouts are designed to promote a continuous, circular flow of traffic. Drivers only need to yield to traffic before entering a roundabout; if there is no traffic in the roundabout, drivers are not required to stop. Because traffic is constantly flowing through the intersection, drivers don't have the incentive to speed up to try and "beat the light," like they might at a signal-controlled intersection.
• One-way travel: Roads entering a roundabout are gently curved to direct drivers into the intersection and help them travel counterclockwise around the roundabout. The curved roads and one-way travel around the roundabout eliminate the possibility of T-bone and head-on collisions.

Design of the new intersection is nearly complete.

Public Works incorporates resident input when feasible. County projects are designed by professional engineers. We balance community input with other considerations to create the best possible final design. Considerations include legal requirements, environmental impacts, budget and safety. Input among residents, user groups and stakeholders often differs. While we do our best to incorporate resident input, we are not able incorporate all input or requests. If you have questions or concerns about the final project design, we invite you to learn more on our website or contact the project manager.

Thank you for joining us for the Northeast 182nd Avenue and Risto Road open house on Aug. 1, 2024. 

Open house recording

Presentation - English (PDF)
Presentation - Spanish (PDF)
Presentation - Russian (PDF)
Presentation - Ukrainian (PDF)