SR 203/High Rock Rd & 203rd St SE – Intersection Improvement

SR 203 is the main highway between Duvall and Monroe. Nearly 12,000 vehicles travel SR 203 at High Rock Road every day, up 10 percent from 2015. Drivers entering SR 203 at the High Rock Road/203rd Street Southeast interchange encounter increasing levels of traffic traveling at speeds up to 55 mph.

WSDOT identified a compact roundabout as a cost-effective solution to improve safety for the ever-growing number of travelers on SR 203.

Roundabouts are an effective intersection type with fewer conflict points and lower speeds, and they provide for easier decision making than other intersection types. Well-designed roundabouts have been found to reduce injury collisions by 75 percent and fatal collisions by 90 percent.

A reduction in maintenance costs, traffic delays, fuel consumption and air pollution are some of the other benefits of roundabouts. They also have a traffic-calming effect by reducing vehicle speeds using geometric design rather than relying solely on traffic control devices.

Compact roundabouts, as the one used in this project, require minimal additional pavement and have completely mountable center islands to make it easier for large trucks to navigate. Compact roundabouts rarely require the purchase of right of way which make them cost-effective.