Bridges

What We Do: Operations, Maintenance and Retrofitting

SDOT owns, inspects, maintains, and/or operates almost 280 bridges.

The goal of the Bridge Program is to extend the service life of our bridges, maintain their historic character, provide safe travel for all, and protect the public’s investment. We achieve these goals efficiently and cost effectively by practicing innovative maintenance management.

Read more below to learn about Seattle’s bridges, how to use them, and how we are working to maintain and improve them. 

An arial photo taken above the Aurora, Fremont, and Ballard bridges, looking west

Pictured: The Aurora, Fremont, and Ballard Bridges 

Bridges and Travel

Some of Seattle's bridges, like the West Seattle Bridge, make connections over bodies of water. Other bridges, like the Magnolia Bridge, are viaducts that make connections over valleys. Some bridges, like the Fremont Bridge, serve all travel modes. Others, like the W Thomas St Overpass, are limited to foot or bike traffic.

Posted vehicle weight restrictions on bridges

Enforcing maximum vehicle loads on bridges is important to maintaining bridge safety and long-term health. See the chart below for current weight restrictions by structure: 

Structure Name Location Weight Restriction
Magnolia Bridge Center, Pier 91 ramps to Port of Seattle on Magnolia Bridge No trucks allowed
McGraw St Bridge McGraw Street over the ravine near 3rd Ave North AASHTO Type 3: 19 tons
AASHTO Type 3S2: 29 tons
Single truck, 4 axle: 17 tons
Single truck, 5 axle: 19 tons
Single truck, 6 axle: 18 tons
Single truck, 7 axle: 18 tons
E Interlaken Blvd East Interlaken Blvd over 26th Ave East 19 tons
Fairview Ave N (southbound) Fairview Ave N between East Galer and E Prospect streets 40 tons
Cowen Park Bridge 15th Ave NE between Cowen Place NE and NE 62nd St Single truck, 7 axle: 36 tons

For information regarding Commercial Vehicle Permits please contact trafficpermitsinfo@seattle.gov, call (206) 684-5086, or visit the webpage

Seattle's moveable bridges

Seattle has seven vehicular, moveable bridges over navigable water. Four of these are owned by SDOT. Federal law requires bridges open for marine traffic, with few exceptions. Seattle is part of the US Coast Guard 13th District. More information is available at www.uscg.mil/d13/

Learn about where these bridges are located and used for vehicular travel below:  

Here is a list of vehicular bridges in Seattle that open for marine traffic:

Moveable bridge Year built Vessel clearance Owned and operated by
Ballard bridge 1917 44 feet SDOT
Fremont Bridge 1917 30 feet SDOT
Montlake Bridge 1925 46 feet Washington State Department of Transportation
Spokane St Swing Bridge 1991 55 feet (at mean high tide) SDOT
South Park Bridge 2014 34 feet (at mean high tide) Owned by King County, Operated by SDOT
University Bridge 1919 42.5 feet SDOT
1st Ave S Bridge

1956, northbound

1996, southbound

39 feet (at mean high tide) Washington State Department of Transportation

To see the current federal regulations around opening the Lake Washington Ship Canal bridges, click here.

Information regarding changes in bridge operations is located on United States Coast Guard Local Notice to Mariners website.

Bridges open on request between 7 AM and 11 PM.

From 11 PM to 7 AM, bridges open by appointment only.  

The average bridge opening, from the time street traffic stops to the time it resumes, lasts about 4 minutes. The Spokane St Swing Bridge openings last about 10 minutes. 

Seattle's Ship Canal Bridges - University, Fremont, and Ballard Bridges - have restrictions in place during the morning and afternoon peak commute to help keep street traffic moving during busy hours. These 3 bridges stay closed to marine traffic on weekdays, from 7-9 AM and from 4-6 PM, except for federal holidays but Indigenous Peoples' Day and for any vessel of 1,000 gross tons or over.  

See the federal regulation for Lake Washington Ship Canal bridges here.

Information on Montlake Bridge openings is available here.

A yacht sails under the open South Park Bridge

Pictured: South Park Bridge

Request an Opening

Between 7 AM and 11 PM: Vessels should contact the bridge by radio (Marine Channel 13), call (206) 386-4251, or use a whistle signal: one long, one short. 

From 7 AM to Dusk: The US Coast Guard requests pleasure vessel use a whistle signal. 

Between 11 PM and 7 AM: Bridge openings are by appointment only and should be requested no less than 1 hour prior to the opening. 

For openings by appointment for the Ship Canal Bridges, the bridge operator will wait 15 minutes after the appointment time before contacting the vessel on Marine Channel 13. If the bridge operator doesn't receive a response, the operator will leave for the next appointment.  

For state- or county-owned bridges, visit www.kingcounty.gov or www.wsdot.wa.gov.

Our moveable bridges operate with complex mechanical and electrical equipment. Though they are rare, issues with these systems can happen. When an outage occurs, our roadway structures crew and engineers work as fast as possible to restore service to the traveling public. To quicken our response, we maintain a Stand-By Crew during weekday off hours as well as weekends and holidays. This crew consists of a lead supervisor, mechanic, and electrician. 

When our roadway structures crew learns of an issue, they take the following steps to get the bridge up and running: 

  1. Deploy staff to inspect and identify the problem.  
  2. Analyze the issue and identify corrective action.   
  3. Some common mechanical issues are traffic control gates or hydraulic fluid pumps not working properly.   
  4. Some common electrical issues are problems with bridge motor controls. These send signals to the control panel in the tower. Or there may be problems with the control panel in the tower, which sends signals to open and close the bridge. 
  5. If the issue is a bad sensor reading, the solution may be as simple as rebooting the system. Other times, we may need more time to diagnose the problem or to get hard-to-replace parts that take several days to arrive and install. In every case, we perform an assessment of each bridge’s many, independent operating systems in a systematic process. This ensures the highest safety and reliability for the repair.  
  6. If the problem is more severe and leaves the bridge out of order for several hours or more, we consult with our traffic control team. We work with them to determine which detours and what signage are needed for short- or long-term bridge closures to meet the needs of commuters during peak traveling hours. 
  7. Once the bridge is working again, we run several tests to verify its operation. The bridge will reopen to the public when we are confident that the bridge is functional and safe. 

Mechanical and electrical systems experience ordinary wear and tear over their service life. We have a strong, proactive maintenance system in place to address these issues and keep our bridges in good working condition.

Experiencing a travel delay related to a moveable bridge or have questions about its status? Follow @SDOTtraffic on Twitter for real-time updates.

A photo of the Fremont bridge as it is getting hosed down with water during a heatwave to keep the steel from expanding. In the foreground, there's a rainbow in the spray of water.

Pictured: The Fremont Bridge over the Lake Washington Ship Canal 

Bridge Maintenance and Improvements

As of 2022, we own, inspect, maintain, and/or operate almost 280 bridges. This is in addition to nearly 1,500 other types of roadway structures—like retaining walls, stairways, and underground support walls. All these structures need ongoing maintenance, inspections, monitoring, and preservation. We are committed to continuing a thorough and proactive asset preservation program. This maximizes the life of our infrastructure so we can rely on it to remain safe and operational.

Bridge program work includes:

  • Bridge Painting Program: Painting steel and other metal on bridges protects them from corrosion and rust. The typical life of bridge paint is 18 years. 
  • Bridge Load Rating Program: Managing and enforcing legal vehicle loads on bridges. This is important for bridge safety and long-term health. Activities include:
    • Analyzing the vehicle load capacity of bridges
    • Field verification tests
    • Monitoring deficient bridges
  • Capital Improvement Program: Besides regular maintenance, some structures may require more significant work or major improvements. Being in a seismically active part of the country, the City also devotes funds to increasing the resiliency of earthquake-vulnerable bridges. These Capital Projects often involve a multi-year planning, design, and construction process. This is completed under our Capital Improvement Program. These investments ensure the City’s roadway structures remain safe and reliable.

Read more below to learn how we’re going above and beyond to maintain, rehabilitate, replace and proactively invest in our bridges: 

Our proactive maintenance approach means we work to prevent issues with our bridges and roadway structures before they happen.

Examples of proactive maintenance include:

  • Regular safety inspections 
  • Removing old paint and repainting bridges. In addition to providing an aesthetic appeal, paint coating protects bridge metal from corrosion and rust due to salt and moisture in the air. Bridges are repainted every 10 to 20 years.  
  • Performing bridge cooling on our moveable bridges. When temperatures reach over 85 degrees three days in a row, we spray our moveable bridges with water to keep them cool. High temperatures can cause bridge steel to expand beyond its operational range, potentially creating problems for a bridge’s opening and closing functions and/or damaging the bridge.    

Check out our blog to learn more in detail how we work to preserve and maintain our bridges to withstand the test of time.

We are actively working on several bridges in the city. Visit the project webpages below to learn more:

Bridge

Updated Status

Admiral Way North Bridge (Seismic Retrofit) Design/Construction 
Admiral Way South Bridge (Seismic Retrofit)  Design/Construction 
Delridge Pedestrian Bridge (Seismic Retrofit)  Design/Construction 
15th Ave NW/Leary Way Bridge (Seismic Retrofit)  Design/Construction 
15th Ave NE over 105th Ave NE (Seismic Retrofit)  Design/Construction 
McGraw St Bridge (Seismic Retrofit)  Design/Construction 
N 41st St Pedestrian Bridge (Seismic Retrofit)  Design/Construction 
33rd Ave W Pedestrian and Bicycle Bridge Design
Ballard Bridge (Bascule) (Seismic Retrofit)  Concept Design (Future Evaluation)
Fremont Bridge (Bascule) (Seismic Retrofit)  Concept Design (Future Evaluation)
1st Ave over Argo RR Bridge (Seismic Retrofit)  Concept Design (Future Evaluation)
4th Ave over Argo RR Bridge (Seismic Retrofit)  Concept Design (Future Evaluation)
4th Ave S Bridge (Main St - Seattle Blvd) (Seismic Retrofit)   Concept Design (Future Evaluation)

Below is a list of completed bridge rehabilitation or replacement projects:   

A photo of the Ballard Bridge, originally made of wood, under construction in 1939

Pictured: Building of the Ballard Bridge, 1939 

A black and white arial photo of the Ballard Bridge over Salmon Bay taken in 1950

Pictured: the Ballard Bridge and Salmon Bay, taken in 1950 

Concrete is poured into a form on the underside of the Ballard Bridge in 2013. The addition of concrete is part of the seismic retrofit project to strengthen the bridge. A photo of the jackets that were installed and then filled with concrete around the columns on the Ballard Bridge in 2013. This is one of the strategies used to strengthen the bridge so that it is better able to survive a major earthquake.

Pictured Left: Concrete is poured into a form on the underside of the Ballard Bridge as part of the seismic retrofit project, 2013.

Pictured Right: Jackets were installed and then filled with concrete around the columns on the Ballard Bridge to strengthen it against earthquake damage, 2013 

A photo of the Ballard bridge taken in 2017

Pictured: Ballard Bridge, 2017