SR 302 Roundabout Pre-design Study

The roundabout project is funded through the Highway Safety Improvement Program (HSIP). The design and construction costs range from $2 million to $3 million for the two-section roundabout. Costs are planning level estimates and are subject to change.

Proposed SR 302 at 118th Avenue Northwest Roundabout Conceptual Drawing

This intersection is offset, which made it difficult to find a proper solution. WSDOT did not consider realignment. This is due to program funding limitations and a desire to make safety improvements sooner rather than later.

The proposed strategy uses two closely spaced roundabouts. The main section has a circular center island, and the second section includes a semi-circular island. Both sections feature raised/drivable surfaces. The roundabout has an 18-foot wide circulating lane. Splitter islands at the approaches and raised shoulders guide vehicles into the roundabout. One of the primary considerations for this design was school buses and freight traveling on 118th Avenue. The design is flexible, allowing the larger roundabout to fit into any future realignment of 118th Avenue.

SR 302 roundabout turning movement options

Number 1, from eastbound SR 302, travelers can choose to:

• Turn right onto 118th Avenue Northwest
• Take the second exit of the roundabout to continue to follow eastbound SR 302
• Take the third exit of the roundabout, turning onto northbound 118th Avenue Northwest
• Make a complete U-turn traveling around both sections of the roundabout in a full circle back to the fourth exit at SR 302

Number 2, from northbound 118th Avenue Northwest, travelers can choose to:

• Turn right onto westbound SR 302.
• Take the second exit of the roundabout by following the second section of the roundabout to southbound 118th Avenue Northwest.
• Access eastbound SR 302 by traveling between the two roundabout sections.
• Make a complete U-turn by traveling between the two roundabout sections back to the fourth exit of the roundabout.

Number 3, from westbound SR 302, travelers can choose to:

• Turn right onto northbound 118th Avenue Northwest.
• Take the second exit of the roundabout to continue to follow westbound SR 302.
• Take the third exit of the roundabout, turning onto southbound 118th Avenue Northwest.
• Make a complete U-turn by traveling between the two roundabout sections back to the fourth exit of the roundabout on SR 302 eastbound.

Number 4, from southbound 118th Avenue Northwest, travelers can choose to:

• Turn right onto northbound 118th Avenue Northwest.
• Take the second exit of the roundabout to northbound 118th Avenue Northwest.
• Take the third exit of the roundabout by traveling past both sections of the roundabout to westbound SR 302.
• Make a complete U-turn by traveling around both sections of the roundabout back to southbound 118th Avenue Northwest exit.

George Mazur
Multimodal Planning Manager
360-357-2651
George.Mazur@wsdot.wa.gov

Debbie Clemen
Study Lead
360-704-3204
Debbie.Clemen@wsdot.wa.gov