West Marginal Way SW Improvements

Updated August 11, 2022

What's Happening Now?

We have continued making improvements on West Marginal Way SW.

  • We built a new sidewalk and finished the Duwamish Longhouse interim crossing signal in December 2021 to provide safer access to those visiting the Longhouse and people walking and biking on the Duwamish Trail. 
  • We made improvements at the West Marginal Way SW and Highland Park Way SW intersection, making it easier and more efficient to navigate the area.
  • We restriped the lane markings along West Marginal Way SW, allowing people driving to see lane markings clearly and overall travel more safely.   
  • We added red painted bus lanes along SW Alaska St to help make bus lanes more visible to drivers and increase compliance with bus only restrictions. 

The new bike lane on West Marginal Way SW will be constructed after the West Seattle Bridge reopens to traffic, expected on September 18, 2022.

  • The new bike lane will complete the all-ages-and-abilities network between South Park and the West Seattle Bridge Trail and beyond, including Alki, the Junction, downtown Seattle, and SODO. It will also enhance safety for everyone along West Marginal Way SW.
  • This announcement came after comprehensive traffic data analysis, which predicts that adding the new bike lane will have minimal effects on the number of trucks that can use the street and how long it takes to drive in the area.
  • Once the bridge reopens we will be collecting traffic data to evaluate and understand new and emerging patterns. Read the update to the community from May 2022.
  • Today, West Marginal Way SW has 3 travel lanes (2 northbound and 1 southbound) and a center turn lane that extend through the full length of the corridor. All three continuous lanes, as well as a center turn lane, will remain open to through traffic until project implementation in 2022.

Project Background

West Marginal Way SW connects communities and industrial businesses along the western bank of the Duwamish Waterway. It is a Major Truck Street between bridges and connects to Port of Seattle facilities. The street also provides direct access to the Duwamish Longhouse and Cultural Center, parks, and residences as well as shipping, manufacturing, and industrial areas. The Duwamish Trail, a multi-use recreational path for people walking and biking, runs alongside West Marginal Way SW for several miles.

Since the closure of the West Seattle Bridge in March 2020, we have seen an increase in the number and speed of people driving on this busy corridor. Due to this detour, average weekday traffic volumes on West Marginal Way SW have increased by over 150%, from 9,760 vehicles to 24,880 vehicles on an average weekday.

This project is designed to make the street safer, more convenient, and more comfortable for everyone, and encourage people walking and biking - our vulnerable users - to use West Marginal Way SW. Each of these improvements can bring us closer to our Vision Zero goals and help to provide alternatives for the traveling public that reduce demands on the road network.

Planned Street Redesign

Graphic showing the lanes on West Marginal Way

Moving freight and goods remains the priority for this major truck street which serves port facilities, cargo yards, and major businesses. We carefully considered this distinction and the importance of maintaining freight reliability during the high bridge closure as we developed the new street design and implementation timeline.

The planned street redesign will further separate vulnerable people from faster-traveling traffic and trucks. This project will also enhance safety for everyone driving by encouraging slower driving speeds, eliminating high-speed passing, improving visibility for people entering from side streets, and improving the predictability of all people using West Marginal Way SW.

This comes after months of engagement with key stakeholders, including our bicycle and freight advisory boards, transportation safety advocates, local businesses, community groups and members, the Port of Seattle and maritime industrial community, and the West Seattle Bridge Community Task Force. The feedback we received from these various groups was mixed. Some asked for the bike lane to be installed this year while others requested installation after the high bridge reopens to traffic. We also considered the Freight Master PlanBicycle Master Plan, our Vision Zero and mode shift goals and data to inform our decision.  

We anticipate installation of the new street design after the West Seattle Bridge reopens. Work can occur on weekends, reducing impacts to freight and general traffic. We expect to maintain one lane of travel in each direction, and to keep nearby driveways open during most of the installation.

Protected Bike Lane 

The 0.6-mile two-way protected bike lane and parking lane will be built on the western side of the street in the southbound lane that begins south of the Chelan 5-way intersection and bridge structures that limit the capacity to West Marginal Way SW.  Redesigning the extra lane, that does not go all the way through the corridor, leads to a smoother and more predictable trip for people driving without unnecessary merging, eliminates high-speed passing, or the need to navigate around slower moving bicycles.

The new bike lane will complement the new sidewalk north of the Duwamish Longhouse and Cultural Center and the walking and biking crossing signal at the Duwamish Longhouse built in fall 2021.

Bike lane project area

Highland Park Way and West Marginal Way Intersection 

In fall 2021, we completed improvements to make the intersection accessible, efficient, and safe:

  • Removed existing raised traffic islands and created a new northbound lane.
  • Shifted the southbound left-turn lanes farther west, providing enough space in the intersection to allow the westbound right turning vehicles (of all sizes) to go at the same time. This improvement will help to reduce wait times at the intersection.  
  • Updated the traffic signal equipment for people of all abilities and installed the infrastructure to allow us to make signal adjustments in real-time remotely from our Transportation Operations Center.
  • Installed new wheelchair-accessible curb ramps in compliance with the Americans with Disabilities Act.
  • Relocated the westbound bus stop.
  • Improved turning movements for people driving through the intersection to shorten wait times.

Duwamish Longhouse: New walking and biking signal, new marked crosswalk, and new sidewalk

People driving fast and higher traffic volumes on West Marginal Way SW can create safety challenges for people trying to access the Duwamish Longhouse. In December 2021, we installed a new, interim crossing signal that stops traffic for people walking and biking who need to cross West Marginal Way SW. A permanent crossing signal is being designed and is scheduled to be installed after the reopening of the West Seattle Bridge.    Graphic showing the Duwamish Longhouse project on West Marginal Way

Pedestrian safety improvements at the Duwamish Longhouse include a new pedestrian signal, crosswalk, and sidewalk.

Reconnect West Seattle Traffic Mitigation 

We made recent improvements to clarify roadway operations as well as encourage good driving habits.   

  • Added a traffic island at West Marginal Way SW in front of SW Front St.  
  • Added white, flexible posts to divide the right turn lane at West Marginal Way SW leading to the on-ramp to the 1st Ave S. Bridge.   

Traffic island and white flexible posts on West Marginal Way SW

(Left) West Marginal Way SW traffic island just north of SW Front St​ and (right) white, flexible posts to divide travel lanes


We are committed to Vision Zero goals of reducing people speeding and injury and fatality crashes in Seattle. In 2020, we installed six speed radar signs along West Marginal Way SW to help reduce travel speeds from 40 mph to 30 mph. We found that the radar feedback signs corresponded with people reducing their vehicle speeds by up to 11% so far.  

Project Timeline 

Early 2021

  • Engaged with area businesses, community partners, and neighbors.
  • Conducted outreach with businesses along West Marginal Way via online business survey
  • Sent a mailer to West Seattle residents about how to give input.  
  • Held a virtual open house. 

Spring 2021

  • Compiled and analyzed feedback

Summer 2021

  • Shared preferred design option with the community.
  • Announced decision to build protected bike lane after the high bridge reopens.

Fall 2021

  • Completed improvements at the West Marginal Way SW and Highland Park Way SW intersection.
  • Built a new sidewalk and finished the Duwamish Longhouse interim crossing signal.  
  • Announced decision to build protected bike lane after the high bridge reopens.

September 2022 (expected)

  • West Seattle Bridge reopens
  • After West Seattle Bridge reopens, begin building West Marginal Way SW improvements 

Community Engagement  

We are committed to working with the community to keep you informed of progress and milestones as we rehabilitate the bridge. We will seek your continued feedback on how to improve mobility and safety for West Seattle, as well as the South Park and Georgetown neighborhoods. Thank you to everyone who has helped us make this project better with your ongoing engagement. 

Learn more, get involved, and tell us what you think:

Watch our project video, available in multiple languages:

Project Materials

Update to community (May 2022)

Bike lane decision blog announcement (7/14/21)

Watch the open house on YouTube (2/18/21)

Open House PowerPoint Presentation (2/18/21)

Open House Summary (2/18/21)

West Seattle Transportation Coalition Meeting Presentation (1/28/21)

Project mailer (English - 1/21) 

Translated project information

West Marginal Way Business Survey (2/4/2021)

Past Outreach Activities