West Marginal Way SW Safety Corridor Project

Updated October 21, 2022

What's Happening Now?

SDOT will be conducting data collection on West Marginal Way SW from Sunday, October 23 – Sunday, November 6. We will close the southbound curbside travel lane for 0.6-miles of the 2.5-mile corridor (from SW Marginal Pl to the Duwamish Longhouse) to collect additional data about SDOT’s proposal to reuse one southbound travel lane for a Protected Bike Lane and on-street parking.   
  
In addition to data collection, the purpose for this lane closure is to test the lane reduction, identify any additional impacts, and compare the results with existing conditions through a safety lens. People walking and biking will not be allowed to use the closed lane during data collection.   
  
This 2-week data collection is part of overall commitment SDOT made to observe what is happening on West Marginal Way SW following the reopening of the West Seattle Bridge. This includes capturing drivers’ speeds, volumes, and driveway turning counts at Duwamish Trail crossings. This information will be used to make decisions about street design and the safety corridor project moving forward.  This evaluation will be published when the analysis is complete.  
 
Please let us know if you have any questions or comments about this by emailing westmarginalway@seattle.gov.

Map of West Marginal Way Southwest with the southbound right lane closure marked between 17th Avenue Southwest to Southwest Alaska Street

Key Accomplishments

  • 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 installed a median island in the center turn lane near SW Front St to ensure good travel behavior.

What’s Left?

Sharing the final analysis results with community, finalizing design of the safety corridor project, and assume implementation in 2023.  
 

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.

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

Diagram illustrating the planned street redesign for West Marginal Way Southwest. It includes a 6-foot walking path protected from the street a 5-foot strip with trees, next to that is an 8-foot bike lane protected from traffic by a 3-foot wide concrete barrier, they the road includes a 12-foot driving lane, an 11-foot center turning lane, two more driving lanes, on 10-feet wide and one 12-feet wide with an 8-foot wide planting strip next to it.

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 project will enhance safety for everyone 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 the West Marginal Way SW corridor. The project will further separate vulnerable people from faster-traveling traffic and trucks and will connect the Duwamish Trail with The West Seattle Bridge Trail.

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 in 2021 while others requested installation after the West Seattle Bridge was open to traffic again. We also considered the Freight Master PlanBicycle Master Plan, our Vision Zero and mode shift goals and data to inform our decision.  

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.

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

Speeding 

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

  • Reopened the West Seattle Bridge

October - November 2022

  • Conduct further data collection and analysis on West Marginal Way SW  

    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