As of June 2026

Status

Phase: Construction complete

On Wednesday, June 24, crews opened two lanes in each direction on 145th Street, including all lanes of the new roundabouts at I-5. This marks the completion of roadwork on the corridor.

 
This aerial photo faces south, showing the two new roundabouts at the 145th Street interchange. Photo by Johansen Construction Company.

Driving the roundabouts

• Slow down to 15-20 miles per hour as you approach.
• Follow the signs and painted road markings to choose the correct roundabout lane for your destination.
• Yield to any traffic already in the roundabout.
• Once inside the roundabout, continue to move without stopping.
• Do not change lanes once inside the roundabout.
• As you prepare to exit the roundabout, use your turn signal to indicate your intended direction.

Visit our roundabouts page Roundabouts page for more information about traveling safely through the roundabouts.

Project Background and History

Get ready for a new way for getting around. Multi--lane roundabouts are coming to the City of Shoreline. The City of Shoreline is building improvements for the SR 523 (N/NE 145th Street) and Interstate 5 (I-5) interchange including NE 145th Street between 5th Avenue NE and the on- and off-ramps on the west side of I-5. The project will replace the signalized intersections on either side of I-5 with roundabouts and update lane configurations on the bridge over I-5. 

A modern roundabout is a circular intersection where drivers travel counterclockwise around a center island. There are no traffic signals or stop signs in a modern roundabout. Drivers entering the roundabout yield to traffic already in the roundabout, then enter the circulating roadway and exit at their desired street, so they function differently from older circular intersection types. Learn more about roundabouts.

The 145th Street and I-5 Interchange Project will improve safety and multimodal access along the 145th Street corridor and help connect to the Shoreline South/148th Light Rail Station. The roundabout improvements will alleviate traffic congestion and enhance transportation mobility, reliability, and safety for all users, including pedestrians, bicyclists, transit, and freight.

Interchange Fly Over

This video illustrates how all modes of travel will move through the roundabouts, including how drivers will travel through the roundabouts along with buses and trucks, and the routes pedestrians and bicyclists will use. The traffic shown in the video reflects the actual, projected traffic volumes at peak commuting hours, and how that volume of traffic will move through the proposed roundabouts.

Project Design

In 2018 and 2019, in collaboration with WSDOT, Sound Transit, City of Seattle, and King County Metro, the City of Shoreline evaluated several alternative design concepts. Through this process, the City and our partners worked to identify a design that would increase safety and efficiency for all travel modes, including cars, freight, transit, pedestrians, and bicyclists. Working in collaboration with multiple stakeholders, the City conducted digital modeling of traffic flows and intersection performance, and even tested a full-scale mockup of the roundabout design using Metro buses.

Initially, the City and our partners considered widening the 145th Street bridge to accommodate people walking and biking, constructing a new northbound I-5 button-hook on-ramp, and installing new traffic lights at the intersections at 5th Avenue NE and the I-5 ramps on the west side of the freeway. However, our analysis showed that multi-lane roundabouts would offer a greater improvement in safety and roadway capacity. Compared to signalized intersections, roundabouts will:

• Improve safety for drivers by decreasing speeds and routing traffic in the same direction, reducing the severity of crashes.
• Improve safety for pedestrians and bicyclists by separating them from vehicle traffic at well-marked and lighted crosswalks and reducing crossing distances.
• Promote continuous traffic flow, reducing overall travel times and minimizing delays along the 145th Street corridor.
• Eliminate the need for left-turn lanes on the bridge, creating space for a two-way, protected bike lane and a 6-foot sidewalk along the north side of the bridge.
• Eliminate the need to widen the existing bridge, substantially reducing construction costs.
• Reduce lifecycle operating and maintenance costs for the two intersections.

These improvements will address todays and future transportation needs and improve safety and access along the corridor for decades to come.

Tree Impacts

This project will have significant tree impacts. We are balancing these impacts with our need to address the biggest contributor to greenhouse gas emissions in Shoreline – transportation. This project helps further our goal of creating dense, walkable communities around transit. For more information on the number of trees removed and their strategic replacement, please see the Tree Impacts section of the 145^th Projects page and the City of Shoreline FAQs about tree impacts.

Project Funding

In November 2021, the State Transportation Improvement Board awarded the project a $5 million grant, which provided the last amount needed to fully fund the $35 million project.

Community Outreach and Involvement

The City of Shoreline conducted the 145th Street Multimodal Corridor Study in 2015-2016 to evaluate current conditions for all users, while considering transportation demands from the new Link light rail station. Through an extensive public process, the City tailored the planned improvements to maximize benefit while keeping community impacts to a minimum.

In fall 2020, the City hosted a virtual open house and an online presentation to share information about the project, answer questions and hear comments. Over 680 people viewed the virtual open house and 99 people attended the online presentation. Participants comments included questions and concerns about traffic flow through the roundabouts, pedestrian and bicycle safety and access, and the importance of maintaining mature trees in the project area.

Design was completed to the 60% level in December 2021.

The City hosted an additional virtual open house in June 2022.

More about Multi-lane Roundabouts

Benefits of Roundabouts

The City of Shoreline’s redesign of the 145th Street and I-5 interchange is based on data that shows the benefits of roundabouts for safety, traffic flow, efficiency, and cost. According to WSDOT traffic studies, roundabout intersections can provide lasting benefits in many ways, including:

• Roundabouts reduce the rate and severity of collisions. Roundabouts reduce the likelihood of collisions by 37%, injury crashes by 75%, fatality collisions by 90%, and pedestrian-car collisions by 40%. Roundabouts also significantly reduce the likelihood of T-bone and head-on collisions.
• Roundabouts calm traffic. Roundabout speeds are usually about 20 mph. Drivers must slow down and yield before entering the roundabout and they are less likely to feel the need to speed up to try to “beat the light.”
• Roundabouts are more efficient. Roundabouts improve traffic flow and reduce waiting time. They facilitate a continuous flow of traffic and can accommodate higher traffic volumes with fewer lanes on the approaching streets.
• Roundabouts are cost-effective. Long-term costs for roundabouts are lower because traffic signal maintenance and electrical costs are not needed. Roundabouts are also more effective during power outages. The cost of building a roundabout is comparable to that of a signal-controlled intersection.
• Roundabouts accommodate all sizes of vehicles. Large trucks, buses, and oversize vehicles can straddle both lanes when driving in a roundabout. Most roundabouts have a truck apron, a raised section of pavement near the center of the roundabout that gives large vehicles extra room to navigate the roundabout.
• Roundabouts are safer for pedestrians and bicyclists. Crosswalks are set back from the intersection, allowing drivers more time to react to pedestrians. Roundabout islands also provide refuge for crossing pedestrians and bicyclists.

Additional Information and Resources

In 2016, the City of Shoreline completed the 145th Street Multimodal Corridor Study and developed a preferred design concept for the corridor from 3rd Avenue NW to Bothell Way NE/Lake City Way (SR 522). Through an extensive public process and thorough technical analysis, the City tailored the planned improvements to maximize benefits while minimizing negative community impacts.

As a result of this study, the City has received federal funding to complete design on two sections of the corridor: this interchange project and the portion of the 145th Street Corridor from Linden Avenue to I-5. Both projects are now being designed.

Additionally, the City has received federal funding for design of a pedestrian/bicycle bridge across I-5 at 148th Street that will connect directly to the new Shoreline South/148th Station. Sound Transit is also in the process of designing improvements on the 145th corridor from Lake City Way to the I-5 interchange to support Bus Rapid Transit (BRT).