Wednesday, July 6, 2022

Coming soon! A new roundabout is being added on SR 500 in Clark County this summer to improve safety, help with traffic flow

By Kayla Dunn

A new compact roundabout is coming to the intersection at Fourth Plain Boulevard, also called State Route 500, and Northeast 182nd Avenue in Clark County to create a safer intersection and keep travelers moving.

On July 11, crews will begin construction on the intersection. Travelers should find an alternate route if possible, or prepare for:

  • single lane closures with alternating traffic near the intersection
  • overnight work
  • a week-and-a-half total closure of the intersection beginning in early August
  • a temporary signal at Northeast 88th Street and Ward Road during the total closure of the SR 500 and 182nd Avenue intersection

The new roundabout is expected to be complete by the end of August. This is one of several projects planned in the area this summer (see more below).

This map shows the new roundabout location at Fourth Plain Boulevard and 182nd Avenue and paving work on SR 500 between Northeast 162nd Avenue and Northeast Leadbetter Road happening this summer.

The roundabout is one of several projects planned in the area this summer (see more below).

Why a roundabout at SR 500 and 182nd Avenue?

This drawing shows the roundabout to be installed at Fourth Plain Boulevard and 182nd Avenue in Clark County.

We decided to install a roundabout based on crash data collected between 2013 and 2017 that showed a history of crashes along this stretch of highway, most of which were rear-end or at-angle crashes, also called T-bone or side impact crashes. A roundabout at this location will improve safety by reducing the potential for these severe types of collisions, while keeping traffic flowing through the intersection.

Studies by the Federal Highway Administration have found that roundabouts can increase traffic capacity by 30 to 50 percent compared to traditional intersections.

Compact roundabouts have a diameter between 65 to 120 feet and are designed so that larger vehicles, like freight trucks or first responder vehicles, can drive over part of the center island to make the turn while still using a relatively small footprint for the roundabout. Compact roundabouts are like single-lane roundabouts, which are slightly larger in size, and use the same design to help keep vehicles, pedestrians and bicyclists moving.

Benefits of roundabouts

There are many benefits of a roundabout, the most important being the reduction in severity of crashes. How does this work? Roundabouts help reduce the likelihood and severity of collisions due to:

  • Low travel speeds. Drivers must slow down and yield to traffic before entering a roundabout. Speeds in the roundabout are typically between 15 and 20 miles per hour.
  • No light to beat. Roundabouts are designed to promote a continuous, circular flow of traffic. Drivers need only 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 do not have the incentive to speed up to try and "beat the light" as they might at an intersection with a traffic signal.
  • 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 minimize any possibility for "T-bone" and head-on collisions.

Other Clark County summer construction

'Tis the season for summer construction in the Pacific Northwest and there are a few other projects happening nearby that we want travelers to know about.

In addition to the roundabout installation, travelers will also notice that other roadwork by WSDOT and Clark County is underway.

There are wild cards in construction this summer including weather and supply chain challenges. For the most up-to-date construction information, travelers can get real-time travel information on the WSDOT website.