Status

Phase: Final Design

The 145th Street and I-5 Interchange project and the 145^th Street Corridor project share a common project boundary at 1st Avenue NE and will be constructed at the same time. Having one general contractor for both projects will improve traffic control through the work zone and will eliminate conflicts having two contractors in the same area. Additionally,  the City should benefit from more competitiveness between bidding contractors with a larger project.

There will be a few pre-construction activities to prepare the site for construction of the Corridor and Interchange project happening soon on NE 145th Street.

• The City will pothole 145th Street on the east and west side of I-5 to locate utilities to complete utility relocations design. 
• Puget Sound Energy (PSE) will also be out this summer to relocate their 8-inch gas main on the west side of I-5 in NE 145th Street from 1st Avenue NE to the I-5 southbound ramps.
• Comcast and Zayo Communications will also be out this summer to relocate the line from overhead power poles to an underground joint utility duct bank east of I-5 on NE 145th Street from 5th Avenue NE to 6th Avenue NE.

Project Overview

The City of Shoreline is designing 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. 

The 145th Street and I-5 Interchange Project will improve safety and multimodal access along the 145th Street corridor and help connect to the future Sound Transit Shoreline South/148th Light Rail Station, planned to open in 2024. The interchange 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 Schedule

The City expects to complete final design and right-of-way acquisition May 2023 and complete permitting May through August 2023 and begin construction in late 2023.

Click image to enlarge.

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 today’s and future transportation needs and improve safety and access along the corridor for decades to come.

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.

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 $30 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 anticipates competition of final design and right-of-way acquisitions by December 2022. To facilitate right-of-way acquisition, the City is currently coordinating with property owners and will continue through the end of 2022.

The City hosted a virtual open house in June 2022. We have gathered your feedback on the 145th Street Corridor and 145th Street and I-5 Interchange projects. Materials from the virtual open house are available below:

• 145th Street Projects virtual open house summary report (PDF)
• 145th Street Projects virtual open house, June 2022 (PDF)
• 145th Street and I-5 Interchange Construction Staging Plan Video (YouTube)
  

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).

The 145th Street and I-5 Interchange Project is one of eight different transportation projects linked to the opening of the Shoreline South/148th Station in 2024. The goal for all these projects is to ensure pedestrians, bicyclists, transit, and auto traffic can get to and from the station as safely and efficiently as possible. Visit the Destination 2024 webpage to learn more about these projects.

Frequently Asked Questions (FAQs)